United States Patent
`Balbinot
`
`[19]
`
`[54] MICROCONTROLLER INTEGRATED
`CIRCUIT WITH READ ONLY MEMORY
`CONTAINING A GENERIC PROGRAM
`
`[75]
`
`Inventor:
`
`Jean-Pierre Balbinot, Le
`Krernlin-Bicetre, France
`
`[73] Assignee: Alcatel Mobile Communication
`France, Paris, France
`
`[21] Appl. No.: 593,283
`
`[22] Filed:
`
`Jan.30,1996
`
`Related U.S. Application Data
`
`[63] Continuation of Ser. No. 272,073, Jul. 8, 1994, abandoned.
`
`[30]
`
`Foreign Application Priority Data
`
`[FR]
`
`France ................................... 93 08626
`
`Jul. 13, 1993
`Int. CI.6
`...................................................... G06F 11/00
`[51]
`[52] U.S. CI .......................................................... 395/182.01
`[58] Field of Search ..................................... 395/180, 181,
`395/182.13, 182.18, 182.16, 182.21, 182.01,
`600; 51650
`
`[56]
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`
`111111111111111111111111111111111111111111111111111111111111111111111111111
`US005590273A
`[111 Patent Number:
`[45] Date of Patent:
`
`5,590,273
`Dec. 31, 1996
`
`4,490,783 12/1984 McDonough et al ................... 364/200
`2/1987 Sacarisen et al ......................... 371116
`4,641,308
`4,797,808
`111989 Bellay et al ..
`5,157,781 10/1992 Harwood et al ..
`5,202,978
`4/1993 Nozuyama ...... : ....................... 395/575
`
`Primary Examiner-Robert W. Beausoliel, Jr.
`Assistant Examiner-Norman M. Wright
`Attorney, Agent, or Finn-Sughrue, Mion, Zinn, Macpeak &
`Seas
`
`[57]
`
`ABSTRACT
`
`A microcontroller integrated circuit comprises a processor
`core which exchanges data with at least one data processing
`and/or storage device. The integrated circuit comprises a
`mask-programmed read only memory containing a generic
`program such as a test program which can be executed by
`the microcontroller. The generic program includes a basic
`function for writing data into the data processing and/or
`storage device or devices. The write function is used to load
`a downloading program. Because a downloading program is
`not permanently stored in the read only memory, the micro(cid:173)
`controller can be tested independently of the application
`program, and remains standard with regard to the .type of
`memory component with which it can be used in a system.
`
`4,435,763
`
`3/1984 Bellay et al. .. ......................... 364/200
`
`20 Claims, 3 Drawing Sheets
`
`MICROCONTRO...LER-BASED SYSTEM
`r------..,
`RAM
`
`REPROM
`
`12
`.--.._/
`17
`
`16
`13
`
`MICRO CONTROLLER
`
`18
`
`19
`
`TEST
`STATION
`
`MASK-
`PROGRAMMED
`ROM
`GENERIC
`TEST PROG.
`
`15
`
`14
`
`1 1 1
`
`110
`
`EXHIBIT 1017
`IPR Petition for U.S. Patent No. 6,249,825
`
`

`

`U.S. Patent
`
`Dec. 31, 1996
`
`Sheet 1 of 3
`
`5,590,273
`
`MICROCONTRQLER-BASED SYSTEM
`...------...
`RAM
`
`REPROM
`
`12
`....-..._/'
`
`17
`
`MICROCONTROLLER
`rr=======~nr+f----.J TEST
`~~~~----1 STATION
`
`14
`
`1 1
`
`110
`
`1 1 1
`
`21
`~
`
`25
`~
`
`26
`~
`
`22
`~
`
`23
`~
`
`24
`~
`
`- -
`
`-
`
`- -
`
`--
`
`16
`1 3
`
`18
`
`19
`
`GENERIC
`~~ TEST PROG.
`
`Fig. 1
`
`GENERIC TEST PROGRAM
`
`MEASURE TRANSMISSION SPEED
`
`POSITION POINTER
`
`READ
`
`WRITE
`
`EXECUTE
`
`Fig. 2
`
`

`

`U.S. Patent
`
`Dec. 31, 1996
`
`Sheet 2 of 3
`
`5,590,273
`
`~~~ANo1fzR czl C1 I Nsl Ns I N41 N31 Nzl N1 I D I
`
`~ '-..r
`
`31
`
`Fig. 3
`
`COMMAND WORD
`~
`
`I szj S1 I daj d?/ dsl ds I d41 d3j dzl d1 I D I
`
`~
`
`41
`
`Fig. 4
`
`TEST STATION TO MICROCONTROLLER
`
`I o I o I o I o I o I o 11 I o ~5,
`I o I o I o I 1 I o I o I 1 I o ~52
`1 o 1 o 1, 1, 1 o 1, 1 o 1 o ~53
`I o 11 I o I 1 I o ,, I, I o ~54
`
`Fig. 5
`
`MICROCONTROLLER TO TEST STATION
`
`1 11 11 I 0 I 0 I 0 I 0 I 0 I 0 ~81 Fig. 8
`
`)
`
`

`

`U.S. Patent
`
`Dec. 31, 1996
`
`Sheet 3 of 3
`
`5,590,273
`
`TEST STATION TO MICROCONTROLLER
`
`MICROCONTROLLER TO TEST STATION
`
`lol,lolololol1111
`
`61
`
`lxlxlxlxlxlxlxlxl
`lxlxlxlxlxlxlxlxl
`
`63
`
`64
`
`65
`
`Fig. 6
`
`TEST STATION TO MICROCONTROLLER
`
`11 I o I o I o I o 11 I o I o ~71
`I o I o I o I o I o I o I o I o 1~72
`I o I o I o I o I o I o I o I o ~73
`I o I o I o I o I o I o I o I o 1~74
`I o I o I o I o I o I o I o I o ~7s
`I o I o I o I o I o I o I o I o ~76
`Fig. 7
`
`

`

`5,590,273
`
`1
`MICROCONTROLLER INTEGRATED
`CIRCUIT WITH READ ONLY MEMORY
`CONTAINING A GENERIC PROGRAM
`
`This is a continuation of application Ser. No. 08/272,073 5
`filed Jul. 8, 1994, now abandoned.
`
`BACKGROUND OF THE INVENTION
`
`2
`the type of fault, i.e. whether it is a physical fault (in the
`microcontroller itself, in an external read only memory, in a
`peripheral device, on a bus, etc) or a software fault (i.e. an
`error in the application program). The troubleshooting tech(cid:173)
`nique usually employed in these cases of total lock-up is
`based on the use of sophisticated test devices requiring the
`application of probes to the pins of the various integrated
`circuits of the microcontroller-based system under test.
`There are various problems associated with the use of
`10 such test devices for troubleshooting a microcontroller(cid:173)
`based system. The probes used in these test devices are very
`fragile, difficult to apply because of the small size of the
`circuit and their close packing, and may not make good
`contact with the circuit.
`Also, because of their high cost, these test devices are not
`mass produced. Consequently, faulty microcontroller-based
`systems cannot be repaired immediately, wherever they
`happen to be located at the time, but must first be returned
`to a place where a test device is available.
`Troubleshooting a microcontroller-based system in this
`way is time-consuming, irksome and costly.
`To avoid the need for direct action on the microcontroller(cid:173)
`based system each time the application program executed by
`the microcontroller of the system is changed, it is standard
`25 practise to use a downloadable read only memory to store
`the application program, a loading program being written
`into a mask-programmed read only memory of the micro(cid:173)
`controller. The mask-progranrmed read only memory of the
`microcontroller is integrated into the microcontroller and
`progranrmed once and for all during manufacture of the
`30 microcontroller.
`To change the application program the microcontroller is
`reset by running the downloading program. This download(cid:173)
`ing program can then communicate with a workstation
`connected to the microcontroller by an appropriate trans-
`35 mission line, this workstation containing the new application
`program to be written into the microcontroller. The down(cid:173)
`loading program receives the new application program and
`loads it into a read only memory external to the microcon(cid:173)
`troller.
`Although this solution avoids the need for direct action on
`the microcontroller-based system (which would entail
`removing from the system the reprogranrmable read only
`memories containing the application program, writing into
`these memories the new application program using an
`appropriate programming device and then replacing them in
`the system), it nevertheless has a major drawback, namely
`specialization of the microcontroller during manufacture.
`Each type of reprogranrmable memory is associated with
`a different downloading program because the programming
`parameters (voltage to be applied, duration for which the
`voltage is to be applied, etc) vary with the technology
`employed. The downloading program is written once and for
`all into the mask-progranrmed internal memory of the
`microcontroller and the latter is therefore restricted to using
`55 memory components of the type for which this downloading
`program was written. In other words, the microcontroller is
`not a standard component and this increases its cost of
`manufacture.
`One object of the invention is to overcome these various
`drawbacks of the prior art.
`To be more precise, an object of the invention is to
`provide a microcontroller circuit which can verify quickly,
`simply, reliably and at low cost the operation of a system
`based on the microcontroller.
`Another object of the invention is to provide a microcon(cid:173)
`troller integrated circuit which can accurately locate the
`
`60
`
`20
`
`1. Field of the Invention
`The field of the invention is that of electronic integrated
`circuits.
`2. Description of the Prior Art
`To be more precise, the invention concerns a microcon(cid:173)
`troller integrated circuit. A microcontroller is usually a VLSI 15
`(Very Large Scale integration) integrated circuit containing
`all or most of the components of a "computer". Its function
`is not predefined but depends on the program that it
`executes, with the result that in respect of potential appli(cid:173)
`cations it is very much a general purpose device.
`A microcontroller necessarily comprises a processor core
`including a command sequencer (which is a device distrib(cid:173)
`uting various control signals to the other components
`according to the instructions of a program), an arithmetic
`and logic unit (for processing the data) and registers (which
`are specialized memory units).
`The other components of the "computer" can be either
`internal or external to the microcontroller, however. In other
`words, the other components are integrated into either the
`microcontroller or auxiliary circuits.
`These other components of the "computer" are data
`processing and/or storage devices, for example read only or
`random access memory containing the program to be
`executed, clocks and interfaces (serial or parallel).
`As a general rule, a system based on a microcontroller
`therefore comprises a microchip containing the microcon(cid:173)
`troller, and a plurality of microchips containing the external
`data processing and/or storage devices which are not inte(cid:173)
`grated into the microcontroller. A microcontroller-based 40
`system of this kind comprises, for example, one or more
`printed circuit boards on which the microcontroller and the
`other components are mounted.
`It is the application program, i.e. the program which is
`executed by the microcontroller, which determines the over- 45
`all operation of the microcontroller system. Each application
`program is therefore specific to a separate application.
`In most current applications the application program is
`too large to be held in the microcontroller and is therefore
`stored in a memory external to the microcontroller. This 50
`program memory, which has only to be read, not written, is
`generally a reprogrammable read only memory (REPROM).
`After the application program has been progranrmed in
`memory and then started in order to be executed by the
`microcontroller, the microcontroller system may not func(cid:173)
`tion as expected.
`In the least unfavorable situation this is a minor dysfunc(cid:173)
`tion of the system and the microcontroller is still able to
`dialog with a test station via a serial or parallel interface.
`This test station is then able to determine the nature of the
`problem and indicate precisely the type of correction (soft(cid:173)
`ware and/or physical) to be applied to the system for it to
`operate correct! y.
`Unfortunately, most dysfunctions of a microcontroller- 65
`based system result in a total system lock-up, preventing any
`dialog with a test station. It is then impossible to determine
`
`

`

`5,590,273
`
`4
`
`3
`defective component or components of a system using the
`microcontroller in the event of dysfunction of the system.
`A further object of the invention is to provide a micro(cid:173)
`controller integrated circuit which avoids the need for direct
`action on the microcontroller-based system to change the 5
`application program, whilst remaining standard as regards
`the type of memory component with which it can be used in
`a system.
`
`SUMMARY OF THE INVENTION
`
`15
`
`clocks;
`peripheral devices.
`The read function is used to verify the content of the read
`only memory storing (or for storing) the application pro(cid:173)
`gram, to test the information acquired by the various periph(cid:173)
`eral devices and, in combination with the write function, to
`test the validity of the random access memory.
`The write function, which advantageously does not use
`any random access memory, is used to validate the various
`10 peripheral devices and the random access memory. It can
`load any program into the random access memory, including
`a more powerful self-test program (after verifying that the
`microcontroller and its environment are capable of execut(cid:173)
`ing the basic functions correctly), or any program for
`downloading the read only memory enabling dynamic adap-
`tation of the microcontroller-based system by modification
`of its application program. The fact that any downloading
`program can be written into random access memory is very
`important because this means that the microcontroller of the
`invention is not restricted to a specific type of memory
`20 component: the microcontroller of the invention is a stan(cid:173)
`dard and therefore low cost product.
`The execute function is used to execute a program written
`in random access memory by the write function.
`The set of three functions can be used to carry out all
`25 kinds of tests and even for troubleshooting during produc(cid:173)
`tion.
`The integrated circuit of the invention advantageously
`comprises communication means implementing a protocol
`for dialog between a generic test program and a test station
`30 connected to said integrated circuit.
`The microcontroller-based system can therefore be
`remotely tested from the test station, the generic test pro(cid:173)
`gram supplying to the test station, on request, full informa(cid:173)
`tion concerning the microcontroller and its environment.
`The group of basic functions constituting said generic test
`program preferably includes measurement of the speed at
`which data is transmitted from said test station so that said
`communication means can match the speed at which data is
`transmitted from said integrated circuit to said speed at
`40 which data is transmitted by said test station. This simplifies
`the test station because it always transmits data at the same
`speed, regardless of the speed at which the microcontroller
`to which it is connected operates.
`Said communication means are advantageously equiva-
`lent
`to a universal asynchronous receiver/transmitter
`(UART; conventionally incorporated in a microcontroller)
`of which only the receive and transmit signals are used.
`Said communication means preferably comprise a serial
`interface and said generic test program receives from said
`test station messages for activating either one of said basic
`functions or a pointer positioning function and sends to said
`test station messages as to the result of activating one of said
`elementary functions. The serial interface is an RS232
`interface, for example.
`Said activation messages are advantageously selected
`from the group comprising:
`messages specifying a predetermined address for a current
`pointer, each message comprising an address specifi(cid:173)
`cation command word in which the number of speci(cid:173)
`fication bytes is encoded and at least one data word
`containing said specification bytes;
`messages to read a memory from the current pointer
`address, each message comprising a read command
`word in which a number of bytes to read is encoded;
`messages to write in a memory from the current pointer
`address, each message comprising a write command
`
`These objects, and others that emerge below, are achieved
`in accordance with the invention by means of a microcon(cid:173)
`troller integrated circuit comprising a processor core adapted
`to exchange data with at least one data processing and/or
`storage device, said integrated circuit comprising a read only
`memory containing a generic program such as a test pro(cid:173)
`gram which can be executed by said microcontroller, said
`generic program including a basic function for writing data
`into said data processing and/or storage device or devices
`and said write function being used to load a downloading
`program.
`The storage and/or data processing devices are either
`integrated into the microcontroller (i.e. into the microcon(cid:173)
`troller integrated circuit comprising the processor core) or
`external to the microcontroller and integrated into separate
`circuits.
`In a preferred embodiment of the invention said read only
`memory containing the generic program is a mask pro(cid:173)
`grammed read only memory, said mask-programmed read
`only memory being programmed once and for all during
`manufacture of said integrated circuit.
`Thus, unlike prior art microcontrollers in which the mask(cid:173)
`programmed read only memory, if any, contains either an
`application program (if this is small) or a downloading
`program (restricted to a specific type of memory compo(cid:173)
`nent), the microcontroller of the invention has a mask(cid:173)
`programmed memory containing a generic program such as
`a test program.
`Accordingly, the microcontroller can be tested with its
`environment, independently of the application program.
`This test can be run either before the application program is
`started or after the application is started if the system in
`which the microcontroller is used fails or is subject to a
`dysfunction.
`In a preferred embodiment of the invention said generic
`program such as a test program comprises a selection of the
`following basic functions:
`reading of data stored by said data processing and/or
`storage device or devices;
`writing of data in said data processing and/or storage
`device or devices;
`executing a program written in said data processing
`and/or storage device or devices.
`The generic program such as a test program can therefore
`be very small in size and thus readily integrated into the
`microcontroller.
`These three basic functions provide for complete testing 60
`of the microcontroller alone or with its environment.
`Said data processing and/or storage device or devices are
`advantageously selected from the group including:
`reprogrammable read only memories, programmable
`more than once after fabrication of said integrated 65
`circuit;
`random access memories;
`
`50
`
`35
`
`45
`
`55
`
`

`

`5,590,273
`
`6
`
`* writing a memory;
`* executing a program.
`
`DETAILED DESCRIPTION OF THE
`PREFERRED EMBODIMENT
`
`5
`word in which a number of bytes to write is encoded
`and at least one data word containing said bytes to
`write;
`messages to execute a program stored in a memory from
`the current pointer address, each message comprising 5
`an execute command word.
`Each of said result messages advantageously comprise at
`least one data word containing read data. In other words, the
`activation messages comprise a command word, possibly
`followed by one or more data words, and the result messages 10
`comprise one or more data words.
`Each command word and each data word advantageously
`comprise at least one start bit, at least one data bit and at least
`one stop bit. This secures transmission of data between the
`generic test program of the microcontroller and the test 15
`station.
`Each of said command words preferably comprises eight
`data bits, as follows:
`two bits encoding the command word type; and
`six bits encoding a number of specification bytes, bytes to
`read and bytes to write, according to whether the
`command word coded in the other two bits is respec(cid:173)
`tively a specification command word, a read command
`word or a write command word.
`In an advantageous embodiment of the invention said
`integrated circuit comprises a pin for starting said generic
`program such as a test program, said generic program such
`as a test program being started when said start pin is excited
`after said integrated circuit has been reset. The start pin is 30
`used to tell the microcontroller that it must switch to test
`mode, i.e. start execution of the generic test program.
`The invention also concerns a method of manufacturing a
`microcontroller integrated circuit comprising a step of etch(cid:173)
`ing a mask-programmed read only memory containing said 35
`generic program such as a test program.
`The invention also concerns an integrated circuit test
`station for testing an integrated circuit of the invention, said
`station comprising means for transmitting activation mes(cid:173)
`sages and receiving result messages. Other features and 40
`advantages of the invention will emerge from a reading of
`the following description of a preferred embodiment of the
`invention given by way of non-limiting example only and
`from the appended drawings.
`
`25
`
`In this description said generic program is a generic test
`program, for example, and said read only memory contain(cid:173)
`ing this generic program is a mask-programmed memory
`programmed once and for all during manufacture of said
`integrated circuit.
`The invention thus concerns a microcontroller integrated
`circuit (referred to simply as a microcontroller in the remain(cid:173)
`der of the description).
`FIG. 1 shows one specific embodiment of a microcon(cid:173)
`troller 11 of the invention and a system 12 based on the
`microcontroller 11.
`In the specific embodiment the microcontroller 11 com-
`20 prises a minimum of components namely:
`a processor core 13;
`a mask-programmed read only memory 14, programmed
`once and for all during manufacture of the microcon(cid:173)
`troller, and
`a UART (universal asynchronous receiver/transmitter) 15.
`The other data processing and/or storage devices enabling
`the microcontroller 11 to operate are external to the micro(cid:173)
`controller 11 in this example, and with the latter constitute
`the microcontroller-based system 12. In this specific
`embodiment the data processing and/or storage devices are:
`a reprogrammable read only memory (REPROM) 16
`which can be programmed more than once after manu(cid:173)
`facture of the microcontroller 11 and is for storing the
`application program executed by the microcontroller 11
`and defining the function of the latter and more gen(cid:173)
`erally the function of the system 12 as a whole;
`a random access memory (RAM) used during execution
`of a program by the microcontroller 11;
`a clock 18;
`two peripheral devices 19, 110.
`Clearly the microcontroller of the invention is not
`restricted to this particular embodiment. Thus, in other
`embodiments, all or some of the data processing and/or
`45 storage devices 16 through 110 can be integrated into the
`microcontroller.
`Likewise, other types of data processing and/or storage
`devices (either internal or external to the microcontroller 11)
`can be used.
`The mask-programmed read only memory of the micro(cid:173)
`controller 11 contains a generic test program.
`In a preferred embodiment, a simplified block diagram of
`which is shown in FIG. 2, the generic test program 21
`comprises a plurality of basic functions including:
`22: reading of data stored in some data processing and/or
`storage devices, such as the reprogrammable read only
`memory 16, the random access memory 17 or the
`peripheral devices 19, 110;
`23: writing of data in some data processing and/or storage
`devices such as the random access memory 17 or the
`peripheral devices 19, 110;
`24: execution of the program written into one of the data
`processing and/or storage devices such as the random
`access memory 17.
`In this embodiment the generic test program 21 also
`comprises two other basic functions, namely measurement
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`FIG. 1 shows a simplified block diagram of a system
`based on one embodiment of a microcontroller of the
`invention, this microcontroller-based system being con- 50
`nected to a test station.
`FIG. 2 shows a simplified block diagram of one embodi(cid:173)
`ment of a generic test program as contained in the mask(cid:173)
`programmed read only memory of a microcontroller of the
`invention.
`FIG. 3 shows one embodiment of the structure of a
`command word exchanged between the test station and the
`microcontroller of the invention as shown in FIG. 1.
`FIG. 4 shows one embodiment of the structure of a data
`word exchanged between the test station and the microcon- 60
`troller of the invention as shown in FIG. 1.
`FIGS. 5 to 8 each show one example of dialog between
`the microcontroller of the invention and the test station as
`shown in FIG. 1, in the following respective cases:
`* positioning a pointer;
`* reading a memory;
`
`55
`
`65
`
`

`

`5,590,273
`
`5
`
`10
`
`15
`
`7
`of a transmission speed (25) and positioning of a pointer
`(26). These functions are described in detail below.
`The generic test program 21 is used to verify and validate
`either the microcontroller 11 alone or the microcontroller 11
`and its environment (i.e. the microcontroller-based system
`12).
`The generic test program 21 is used to test and validate
`each of the components constituting the microcontroller(cid:173)
`based system.
`The correct operation of the microcontroller alone can be
`verified in a first phase, i.e. before it is introduced into the
`system 12 in order to cooperate with the data processing
`and/or storage devices 16 through 110. The correct operation
`of the system 12 as seen by the microcontroller can be
`verified in a second phase.
`These two preliminary test and validation phases do not
`require the presence of an application program in memory
`(read only memory 16 or random access memory 17). All
`that is required is to tell the microcontroller 11 that it must
`switch to test mode, in which mode it executes the generic 20
`test program (as contrasted with the normal operating mode
`in which it executes the application program contained in
`memory). In one specific embodiment of the invention the
`microcontroller 11 comprises a start pin (not shown) and the
`generic test program is started when this start pin is excited
`after the microcontroller has been reset.
`Note that the microcontroller 11 and its environment
`(external devices 16 through 110) can also be tested and
`validated in the event of a dysfunction of the system 12
`during execution of the application program.
`Finally, the write basic function 23 can write into random
`access memory a test (or self-test) program that is more
`complex than the generic test program 21 but whose correct
`execution presupposes that the microcontroller 11 and its
`environment are operational in respect of execution of the 35
`basic functions 22 through 24.
`The application program, i.e. the program executed by the
`microcontroller 11 and which confers its function on it, is
`usually written into a memory after the microcontroller 11
`and its environment have been tested and validated.
`The generic test program 21 of the microcontroller of the
`invention offers various ways to store the application pro(cid:173)
`gram in memory.
`A first way is to store the application program directly in
`random access memory 17 using the write basic function 23. 45
`A second way, offering better performance because it is
`durable, consists in storing the application program indi(cid:173)
`rectly in read only memory 16 and storing beforehand in
`random access memory 17 a program for downloading this
`read only memory 16. Clearly any type of downloading 50
`program (and thus any type of reprogrammable memory)
`can be used because the generic test program writes it into
`the random access memory 17 like any other program (in
`other words, the content of the program written is transpar(cid:173)
`ent insofar as the write function 23 of the generic test 55
`program 21 is concerned). The microcontroller 11 of the
`invention can therefore adapt dynamically to its application
`context (through the facility for downloading of the read
`only memory) whilst remaining a standard product (in that
`there is no limitation as to any specific type of reprogram- 60
`mabie memory).
`Referring to FIG. 1, the microcontroller 11 is usually
`connected to a test station 111, by an RS232 serial link, for
`example. To this end the microcontroller and the test station
`each comprise communication means for implementing a 65
`dialog protocol. The test station 111 is a microcomputer, for
`example.
`
`8
`In the specific embodiment of the invention shown in
`FIGS. 1 and 2 the generic test program 21 comprises a basic
`function 25 for measuring the transmission speed from the
`test station 111. The transmission speed of the communica-
`tion means 15 of the microcontroller 11 is then made equal
`to that of the test station 111, and is therefore independent of
`the clock 18 of the system 12. The communication means 15
`are equivalent to a UART (Universal Asynchronous
`Receiverffransmitter), for example, of which only the
`receive signal Rx and transmit signal Tx are used.
`One example of a protocol for exchange of data between
`the microcontroller 11 and the test station 111 is now
`described with reference to FIGS. 3 through 8.
`The test station 111 sends to the microcontroller 11
`messages to activate one of the following four basic func-
`tions: read 22, write 23, execute 24 and position a pointer 26
`of the generic test program 21.
`In return, the generic test program 21 sends the test station
`111 messages as to the result of activating one of said basic
`functions.
`An activation message comprises a command word, pos(cid:173)
`sibly followed by one or more data words. A result message
`comprises one or more data words.
`FIG. 3 shows one embodiment of the structure of a
`command word. In this example a command word com-
`25 prises a start bit D, a data byte 31 comprising six bits N1
`through N6 encoding the command word type and two stop
`bits S1, S2.
`The codes for the command word type are as follows:
`00: position pointer command 26;
`01: read command 22;
`10: write command 23;
`11: execute command 24.
`FIG. 4 shows one embodiment of the structure of a data
`word. In this example a data word comprises a start bit D,
`a data byte 41 and two stop bits S1, S2.
`The number coded in binary in bits N1 through N6 is one
`less than the number of bytes to be coded (N) (i.e. N-1).
`The number N to be coded is:
`a number of bytes in which is specified the address at
`which a current pointer must be positioned in the case
`of a pointer positioning command word;
`a number of bytes to be read from the current pointer
`address in the case of a read command word;
`a number of bytes to be written from the current pointer
`address in the case of a write command word.
`Each of FIGS. 5 through 8 shows one example of dialog
`between the microcontroller of the invention and the test
`station. To simplify the diagrams only the data bytes are
`shown (the start bits D and the stop bits S1, S2 do not convey
`any data).
`FIG. 5 shows the situation of specification by the test
`station of an address to which the current pointer of the
`microcontroller is to be positioned, the address specified
`being the memory address from which one of the three basic
`functions (read, write, execute) is to be executed.
`In this example the address specified is 123456 and each
`digit specifying the address is coded on four bits.
`Accordingly the test station first sends a command word
`S1 indicating that this is a pointer positioning command
`(C2C1=00) and that the address is coded on N=3 bytes (N6
`to N1=(10) binary=2=N-1), followed by three data words 52
`through 54 containing the address (0001, 0010, 0011, 0100,
`0101 and 0110 respectively corresponding to the coding of
`1,2,3,4,5 and 6).
`FIG. 6 shows the situation in which the test station
`commands reading of bytes by the microcontroller from the
`current pointer address.
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`In this example the station sends a command word 61
`indicating a read (C2C1=01) and that there are N=4 (N6 to
`N1=(11) binary=3=N-l) bytes to read. The microcontroller
`then sends the test station the four data words 62 through 65
`containing the data read (bits denoted x to indicate any 5
`value).
`FIG. 7 shows the situation of the test station commanding
`writing of bytes by the microcontroller from the current
`pointer address.
`In this example the test station first sends a command
`word 71 indicating a write (C2C1=10) and that there are
`N=5 (N6 to N1=(100) binary=4=N-l) bytes to write, fol(cid:173)
`lowed by five data words 72 through 76 containing the data
`to be written (0 for all the bits in this example).
`FIG. 8 shows the situation of the test station commanding
`execution by the microcontroller of a program stored from 15
`the current pointer address. Accordingly, the test station
`sends a command word 81 indicating execution (C2C1=11).
`The invention also concerns a method of manufacturing a
`microcontroller integrated circuit as described above by
`means of one specific embodiment. This method comprises 20
`a step of etching the mask-programmed read only memory
`containing the generic te