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L4450A 64-Bit Digital I/O with Memory and Counter 8
L4400 User’s Guide 209
Optionally, you can provide an external strobe input on the H2 line to control
the memory transfers. If you pace the memory inputs from an external clock,
the L4450A will sense the leading edge of the strobe and set the data. The data
will be valid after T
PD
and the receiving device may latch the data. T
PD
ranges
from 140 ns to 60 ns. The maximum T
PD
of 140 ns limits operation in this
mode to 7 MHz.
A synchronous buffered output using an external clock is shown in the
diagram below (default handshake line polarity).
For example, using the internal strobe, the following SCPI commands set
the L4450A to have a 32- bit output using synchronous handshake. The number
of times to output the traces is set to 4. A trace is then loaded into memory and
assigned to the channel. The memory is enabled and then triggered. The
start/stop line is set high following the first byte handshake and remains high
until the last byte is output.
CONF:DIG:WIDT LWOR, (@1101)
CONF:DIG:DIR OUTP, (@1101)
CONF:DIG:HAND SYNC, (@1101)
SOUR:DIG:MEM:NCYC 4, (@1101)
TRAC:DATA:DIG:LWOR (@1101), mytrace, #hFFEEFFEE, #hBCBC9999
SOUR:DIG:MEM:TRAC mytrace,(@1101)
SOUR:DIG:MEM:ENAB ON, (@1101)
SOUR:DIG:MEM:STAR (@1101)
Using an external strobe, the following SCPI commands set the L4450A to
have an 8- bit output using synchronous handshake with an external strobe
input. The number of times to output the traces is set to infinite (continuous
output until the memory is stopped). The memory is enabled and then
triggered. The start/stop line is set high following the first byte handshake and
remains high until the last byte is output.
CONF:DIG:WIDT BYTE, (@1101)
CONF:DIG:DIR OUTP, (@1101)
CONF:DIG:HAND SYNC, (@1101)
CONF:DIG:HAND:SYNC:STR:SOUR EXT, (@1101)
SOUR:DIG:MEM:NCYC 0, (@1101)
TRAC:DATA:DIG:BYTE (@1101), mytrace, 260, 139
SOUR:DIG:MEM:TRAC mytrace,(@1101)
SOUR:DIG:MEM:ENAB ON, (@1101)
SOUR:DIG:MEM:STAR (@1101)
H0 (Start/Stop)
H2 (Clock In)
Data Out
Valid
T
CYCLE
(Last Cycle)
Invalid
T
PD
T
PD
T
PD