Fluke PM-3390B, PM-3380B, PM-3370B, PM-3394B, PM-3384B user manual ’Array of 512 integers

3 - 32 USING THE COMBISCOPE INSTRUMENTS

3.4.3.1Conversion of 8-bit samples to integer

As an example a conversion of a trace of 512 "8-bit" samples is shown. The format is as follows:

trace bytes

# 3 5 1 4 <8> <byte 1> . . . <byte 512> <checksum> <NL>

trace sample 512 trace sample 1

byte with decimal value 8 number of trace bytes (514) number of digits of 514

PROGRAM EXAMPLE:

In this example a trace acquisition of 1 byte samples is done. Thereafter, the trace data is read and converted to integer samples in the array "trace", and the number of trace bytes and trace samples is printed. The conversion from single byte value to integer is done as follows (refer to figure 3.12):

If byte ≥ 128 then integer = byte - 256.

Example: byte = 255 --> integer = 255 - 256 = -1.

DIM trace(512)		’Array of 512 integers
DIM response AS	STRING * 520	’Trace response buffer
CALL Send(0, 8,	"*RST", 1)	’Resets the instrument
CALL Send(0, 8,	"FORMat INTeger,8", 1)	’Data format of 8-bits samples
CALL Send(0, 8,	"INITiate", 1)	’Single shot initiation
CALL Send(0, 8,	"*WAI;TRACe? CH1", 1)	’Queries for channel 1 trace
CALL Receive(0,	8, response$, 256)	’Reads the channel 1 trace
PRINT "Number of read bytes ="; IBCNT%		’IBCNT% = number of read bytes

’

’The contents of the response$ string of this example will be as follows:

’ # 3 5 1 4 <8> <byte 1> ... <byte 512> <checksum> <10> ’<10> is terminating LF

’

nr.of.digits = VAL(MID$(response$, 2, 1))

nr.of.bytes = VAL(MID$(response$, 3, nr.of.digits)) - 2 PRINT "Number of trace bytes ="; nr.of.bytes sample.length = ASC(MID$(response$, 3 + nr.of.digits, 1)) nr.of.samples = nr.of.bytes / (sample.length / 8)

PRINT "Number of trace samples ="; nr.of.samples

FOR i = 1 TO nr.of.samples

trace(i) = ASC(MID$(response$, i + 3 + nr.of.digits, 1)) IF trace(i) > 127 THEN

trace(i) = trace(i) - 256

END IF NEXT i