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This application note describes a very simple method of capturing and storing eight lines of digital information, much like a digital logic analyzer. No additional hardware is necessary, and to keep the routine simple, only the main FT-100 unit is used for the digital input as well as the trigger source. Once the digital information is captured and stored in memory, you are free to treat the data as your needs dictate. The data may be stored on a disk file, printed out, downloaded to a computer, or analyzed for specific features and later discarded.

Features

- Uses no additional hardware. Main FT-100 unit is used for all capture and trigger functions.
- Several triggering options are available:
- No triggering (free running)
- Digital Input Line (main unit only)
- Logic Word matching
- Externally gated data
- Trigger polarity may be positive- or negative-going
- Number of samples recorded may be specified, and is limited only by the amount of available
   memory in the FT-100. (The routine indicates the available memory.)
- Time between each sample is programmable.
- Data may be stored on a floppy disk
- Data may be stored in an array for analysis by the FT-100 program.
- Normally, several thousand data samples can be stored (up to over 60,000!).

Limitations

- Only 8 lines of data are captured.
- The only Digital Input Port used to capture data is PA10.
- The smallest sample speed allowed is 8 msec. per sample.
- The time between each sample is always in increments of around 2.8 msec.
- If data is externally gated in, the recycling time is about 11.6 msec.
- During data capture, the FT-100 cannot perform other tasks. The FT-100 will remain in the
    assembly routine until all the data is captured.
- All timing is based on the microprocessor crystal, and may not be accurate enough for some
    very high-accuracy applications.
- Externally gated data relies on a software trigger. This causes a small delay between the
    trigger and the captured data (usually less than one msec.).
- All internal interrupts are enabled during data capture. If this is a problem, disable interrupts
    using the DINT command prior to calling the assembly subroutine.

To maximize speed, the data is captured and stored by an assembly subroutine. The accompanying program READ's and POKE's each assembly byte into the FT-100 memory. Triggering is also done inside the assembly subroutine. All input information is passed to the assembly subroutine through specified, and fixed, RAM locations. The data is captured and placed in RAM beginning at the RAM location indicated by BEG_ADDR. All data is stored in byte format (binary) as input from the Digital Input Port (PA10), and may be retrieved by using the PEEK command.

Once the assembly routine has been "poked" into memory and the input parameters "poked" into their designated RAM locations, the assembly subroutine may be called by using the SYS command. Any time you wish to capture and store digital data, simply call the subroutine. The input parameters, as well as the assembly program, will remain in RAM and will not be changed as long as the main program remains running. If the program is stopped or ends, the information will still remain in RAM, and may be accessed directly (in the Direct Command mode). If a different program is loaded into the FT-100, anything previously in RAM memory will not be valid.

CAPTURING DIGITAL DATA

Once the assembly subroutine is poked into memory, it may be called anytime, using the SYS command. The actual memory location of the assembly subroutine is indicated by the variables PROG_SEG and PROG_OFF. Prior to calling the assembly subroutine, the input parameters must be established and passed to the subroutine through the designated RAM locations. Once the parameters are placed in RAM, they will remain valid and need not be reset unless your program changes a value. Following are the input parameters and a description of each:

ACCESSING THE DATA

The digital data is stored in RAM beginning at the location indicated by the variable BEG_ADDR. The data may be accessed by using the PEEK command. Data is stored in binary format, just as it is read from Digital Input Port PA10. The program listing shows a method of storing the data on a disk file. What you choose to do with the data after it is captured is completely up to you. The data will remain valid in RAM until more data is captured.

When keying in this program, the comments may be omitted. They are there only for clarification. Also, use care when entering the DATA statements (assembly subroutine). They must be exact for the subroutine to function properly.

LOGIC_1 'Program Name
'
     PROG_LEN= 93H 'Number of bytes in assembly subroutine
'
'---- Find location in RAM to place assembly routine ---
     LAB_BEG=PEEK 45+(PEEK 46*256)+((PEEK 47+(PEEK 48*256))*16)
     STR_BEG=PEEK 59+(PEEK 60*256)+((PEEK 61+(PEEK 62*256))*16)
     MEM_FREE = LAB_BEG-STR_BEG-16          'Free memory available for assembly program
     PROG_SEG=INT (STR_BEG/16)+1
     PROG_OFF=0
     ADDR=PROG_SEG*16
'
'--- Test for enough memory ---
     IF PROG_LEN>MEM_FREE THEN BEEP:CLS:DISP "INSUFFICIENT":DISP "MEMORY!":END
'
     FOR I=0 TO PROG_LEN:READ X:POKE (I+ADDR),X:NEXT 'Load assembly program
'
'----------------------------- Assembly Program -----------------------------
     DATA 006H,02BH,0FFH,0FCH,0BEH,077H,001H,08AH
     DATA 014H,046H,08BH,01CH,046H,046H,08BH,02CH
     DATA 046H,046H,08BH,00CH,046H,046H,0FFH,034H
     DATA 007H,0F6H,0C7H,040H,074H,00EH,0F6H,0C7H
     DATA 020H,075H,044H,0E4H,004H,03AH,0C3H,075H
     DATA 0FAH,0EBH,02EH,090H,0F6H,0C7H,020H,074H
     DATA 026H,051H,02AH,0F6H,08AH,0CFH,080H,0E1H
     DATA 007H,0B4H,001H,0D2H,0E4H,0ECH,022H,0C4H
     DATA 08AH,0E8H,0ECH,022H,0C4H,03AH,0C5H,074H
     DATA 0F9H,08AH,0E8H,0F6H,0C7H,080H,075H,002H
     DATA 032H,0C4H,03CH,000H,075H,0ECH,059H,0E4H
     DATA 004H,0AAH,0E2H,002H,007H,0CBH,08BH,0C5H
     DATA 02DH,001H,000H,075H,0FBH,0EBH,0F0H,051H
     DATA 08AH,026H,080H,000H,080H,0E7H,080H,0B1H
     DATA 004H,0D2H,0EFH,059H,00AH,0E7H,080H,0CCH
     DATA 004H,088H,026H,080H,000H,08AH,0C4H,024H
     DATA 0FBH,0E6H,005H,08AH,0C4H,0E6H,005H,0E4H
     DATA 006H,0D0H,0E0H,073H,0FAH,0E4H,004H,0AAH
     DATA 0E2H,0EBH,0EBH,0C8H
'---------------------------------------------------------------------------------------
'
'----- Set Input parameters before calling the Digital Capture subroutine -----
'
     TRIG$ = "LA41" 'Trigger line ("EXT"=external, ""=none)
     SAMPLES = 1000 'Number of samples of data to store
     TIME_DIV = 150 'Time delay between each sample (msec)
     TRIG_POL = 0 'Trigger polarity (0=pos, 1=neg)
'
'----- Test for enough memory to store waveform -----
     MEM_DATA = MEM_FREE - PROG_LEN              'Memory available for data storage
     IF MEM_DATA<SAMPLES THEN CLS:BEEP:DISP "INSUFFICIENT":DISP "MEMORY!":END
'
'---- Place Input parameters in memory locations for Digital Capture subroutine to use
'
     DATA_SEG=INT(PROG_SEG+(PROG_LEN/16)+1)           'Location for data storage
     POKE 17EH,(DATA_SEG-(INT(DATA_SEG/256)*256))     '(LSB) STORAGE SEG.
     POKE 17FH,DATA_SEG/256                           '(MSB)
'
     POKE 17CH,(SAMPLES-(INT(SAMPLES/256)*256))       '(LSB) Number of samples
     POKE 17DH,SAMPLES/256                            '(MSB)
'
     COUNT=INT((TIME_DIV-8.1)/2.8114+0.5)+1
     POKE 17AH,(COUNT-(INT(COUNT/256)*256))           '(LSB) Sample delay
     POKE 17BH,COUNT/256                              '(MSB)
'
'----- TRIGGER INFO -----
     IF TRIG$="" THEN POKE 179H,0:GOTO L0             'No trigger
'
     IF TRIG$="EXT" THEN POKE 179H,(60H OR (TRIG_POL*80H)):GOTO L0    'External trigger
'
     IF LEFT$(TRIG$,1)="L" THEN GOTO L1               'Line trigger?
     POKE 179H,40H:POKE 178H,VAL TRIG$                'Word trigger
     GOTO L0
'
' ----- LINE TRIGGER -----
L1: TR_LINE = VAL(RIGHT$(TRIG$,(LEN(TRIG$)-2)))      'Trigger line#
     TR_PORT = INT ((TR_LINE-1)/8)                    'Trigger Port#
     POKE 177H,TR_PORT-5
     X=(TR_LINE-1)/8
     POKE 179H,((X-INT X)*8) OR 20H OR (TRIG_POL*80H)
'
L0: SYS PROG_SEG,PROG_OFF               'Call assembly routine to capture data
'
     BEG_ADDR=DATA_SEG*16               'Location of the beginning of the stored data
'
' At this point the captured digital information is in memory (in binary format)
' beginning at memory location BEG_ADDR. If the waveform is to be saved to a disk file,
' use the following routine:
'
'----- Store captured digital information to a disk file (optional) -----
'(Note: If SAMPLES is larger than 32767, two loops must be used)
     OPEN "DIGITAL.DAT",OUT
     FOR I=0 TO (SAMPLES-1)
     STORE PEEK(I+BEG_ADDR)
     NEXT
     CLOSE
/

NOTICE:  Every effort has been made to insure the accuracy of the information contained in this document, however
                   Y-tek is not responsible for any consequences resulting from erroneous or inaccurate information.

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FT-100a Functional Tester

Custom-Designed Test Systems

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