NATIONAL INSTITUTE FOR NUCLEAR AND HIGH ENERGY PHYSICS  DEPARTMENT OF ELECTRONIC TECHNOLOGY  P.O.box 41882, NL 1009 DB AMSTERDAM

 

LPT_JTAG

Hard- and software to drive JTAG compatible ports  version: may 20 1998

 

  
The LPT_JTAG software is a program written in QBASIC. It takes a datafile as an input, generates a few output files and drives the LPT port. A special (home made) cable from the PC's LPT-port to the JTAG port is required.

Check for most recent version: http://www.nikhef.nl/user/d01/lpt_jtag/ 

Fast access to chapters:

General Commands Example Example 2 Software Hardware TAP controller

LPT_JTAG interface.

The LPT_JTAG software is a small program written in QBASIC. It takes a datafile as an input and generates a few output files. A special cable from the PC's LPT-port to the JTAG port is required.

Please note that in this version of the Basic program, the cable specification has changed. This is done to minimize (remove) the cross-talk between TDO and TCK. Especially TCK is very sensitive to noise. At NIKHEF we use long cables and RS 485 translators to access self programmed JTAG ports. In the past we had problems with cross-talk from TDO to TCK. If you are using this stuff already, you have to swap pins 2 and 8 on the D25 connector. Use this connector specification with software of May 1 1998 or later.

The program takes the <name>.idt input file from the data subdirectory and checks the syntax. <name>.log is generated, containing the original statements and the expanded loops. Endless loops will run until a key is hit. Endless loops are defined by omitting the number of loops. The logging is limited to showing the complete sequence once. The data read back is recorded 4 times in the <name>.log file. The data received is represented in binary format. Loops cannot be nested. When the input data is entered in hexadecimal format it is converted into a multiple of 4 bits. Hexadecimal data should start with '0X' or '$'. A comment starts with ';', the rest of the line is ignored by the parser. There is no difference between upper and lower case. The <name>.odt file just holds the data send and received in binary format. The <name>.err file lists the syntax errors with the corresponding line numbers in the source file (<name>.idt). If multiple input files are run after another, the line numbers are not reset.

With the last data bit transmitted, also TMS must be set, see IDAT.

 
 

Example: 

test.idt	meaning	test.log
TMS0,rst1, rst0	make TMS low, make TRST high, make TRST low	1 TMS0,rst1, rst0
TMS1,tms2 ; flut	make TMS high, make tms two -> syntax error. flut is a comment	2 TMS1,tms2 ; flut  syntax error: >TMS2< in line 2
loop	Start of an endless loop	3 loop  --- begin_loop 0  (endless loop)
idat 010101010101	binary data to be send, LSB first.	4 idat 010101010101  read 1 > 111111111111
trg1,trg0	set and reset triggerbit	5 trg1,trg0
endl	end of the loop, exit here when a key is hit	6 endl  read 2 > 111111111111  read 3 > 111111111111  read 4 > 111111111111  --- manual end_loop  (executed 55 times)
idat $2a7bcdef	hexadecimal data to be send (2 is converted to 0010)	7 idat $2a7bcdef  read > 00101010011110111100110111101111
loop 3; all devices	loops the statements up to 'endl' 3 times	8 loop 3; all devices  --- begin_loop 3
tms1		9 tms1
TMS0		10 TMS0
endl		--- loop 2  9 tms1  10 TMS0  11 endl  --- loop 1  9 tms1  10 TMS0  11 endl  --- end_loop
tms1,tms0		12 tms1,tms0
rst1,rst0		13 rst1,rst0

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Example 2

The line numbers are incremented while the program is running. This useful when a number of input files are run after another.

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The software is written QBASIC because this gives easy access to the LPT port and because I am not a software expert. lpt_jtag.bas can be run in a DOS-window in Windows. Using lpt_jtag.pif the program can conveniently be started via an icon. Adjusting the file properties, the proper default subdirectory (location of the program) should be defined. The Basic program searches for input files in the subdirectory data. The output files are stored in the same subdirectory. You must correct the path definition in the beginning of the program. This is where it says: dir$="D:\HENKG\JTAG\DATA".
For a specific use at NIKHEF, the <name>.log file can be converted to a file set into the subdirectory data\vme\. This option becomes available at the end of a series of input files. It is not likely this is of any use outside our institute.

TMS
TMS is used to step through the TAP-controller. I choose to do this on a low level (instead of go from idle to shift_dr) to have full control over my programmed JTAG ports.

RST
RST is (hardly ever) used to reset the TAP-controller. I advise you not to use it if possible.

PEN
Program enable is foreseen to be used with MACH devices. The program enable pin on these chips enables the JTAG port to load a new functionallity (to re-program them).

TRG
TRG can be used as a trigger to the oscilloscope when debugging the system under test. It is not used in the connector on the board under test.

UNI
UNI is used at NIKHEF to generate test pulses to our boards. A sort of general purpose signal. Much like TRG.

LOOP
LOOP creates a loop as in Basic. The ENDL defines the end of the sequence to be looped through. Without parameters it is an endless loop, untill a keyboard input is seen (Enter). A parameter defines the number of loops (decimal). Loops cannot be nested. The rest of the line, containing the loop statement, is ignored. So, don't put anything else then a comment there. In an endless loop the generation of <name>.ODT and <name>.LOG is paused after three loops and continued when the loop is left.

WAIT
WAIT stops execution of the <name>.idt file untill user input (Space). When a parameter is used, it defines the number of seconds to pause (decimal).

IDAT

The IDAT command sends data to the device under test and reads back the results from the device. When hexadecimal data is specified, always a multiple of 4 bits are generated. With the last bit transmitted, TMS is set high according to the 1149 specifications. The last bit is shifted when the TAP controller goes from shift to exit1, either in instruction or data mode. For long registers, a single data string might not be very convenient. For this reason multiple idat commands can be given. The concatenation character '+' prevents the automatic TMS generation here.

So the command:

When in the VSYS mode some commands are ignored: PEN0, PEN1, TRG0, TRG1, BYP0, BYP1 and WAIT. Loops are expanded in the usual way and endless loops will generate (large) files, until stopped manually. The file generated is named <name>.do, the usual extension for a simulator macro file. The ESYS command ends the generation. Multiple VSYS-ESYS sequences may be used to build the macro.

TMON
The TMON command switches the tap monitor on and off. When a command line is fully executed and echoed in the .log file, the current TAP-state is added to the .log file in the same line between < > brackets.
Example:

;vsys
loop 2
tms1, tckn 5 ; reset
tms0,tms1,tms1,tms0,tms0 ;reset to shift_ir
idat 0101; Card number, should read 0001
tms0,

card.log, created: 10-31-1997 11:47:26
Software version: october 31th 1997
 1   ;vsys <reset>
 2   loop 2
--- begin_loop  2  <reset>
 3   tms1, tckn 5 ; reset <reset>
 4   tms0,tms1,tms1,tms0,tms0 ;reset to shift_ir <shift_IR>
 5   idat 0101; Card number, should read 0001
     read 1111  (implicit TMS1 sent with last bit) <exit1_IR>
 6   tms0, <pause_IR>

; Read hits via majority control register

tms1,tms1,tms0,tms0; idle to shift_ir

idat 1111 1111 1111+; TDC4,5,6: bypass
idat 1111+; Control chip: bypass
idat 0011+; Majority chip: control
idat 1111; Read out chip: bypass

tms0,tms1,tms1,tms1,tms0,tms0; shift_ir to shift_dr

idat 000+; TDCs: bypass
idat 0+; Control chip: bypass
echo even channels pulsed, threshold = 48
log1
idat 0010 0000+; Majority: control, enable driver
echo 0010 0100 expected
log0,wait
idat 0; Read out: bypass

tms0,tms1,tms1,tms0; shift_dr to idle

?,!
The question mark "?" asks the user to input a parameter. This either decimal or hexadecimal. At NIKHEF we use it to define the address of the card on the bus to be accessed. The exclamation mark "!" is used to pass the parameter to the chain.
Example:
 

log0
tmon1
byp0
tms1,tckn 4,tms0
? Card address
sadd !
tms1,tckn 4,tms0
sadd !
tms1,tckn 4,tms0; go to idle

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At NIKHEF we defined a 10 pin header to connect the LPT cable.
 

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Since you can never find the TAP controller's state diagram when you need it, here it is.