Agilent Technologies L4400 - Manual (Page 217)

L4450A 64-Bit Digital I/O with Memory and Counter 8
L4400 User’s Guide 205
Synchronous Handshake Mode
In the synchronous handshake mode, a strobe or clock signal is used to
transfer data to or from an external device. The strobe line (H1) is an
output and is pulsed once for each transfer.
Synchronous Unbuffered Inputs For synchronous handshake unbuffered
inputs the H0 line indicates the direction of the transfer. This line is set
high to indicate an input operation. The H0 line will remain in the high
state until the L4450A direction is changed. The H1 line is the strobe
output line. The H2 line is not used and is set to high impedance.
The timing of the input operation is controlled by the T
CYCLE
parameter
set using the CONFigure:DIGital:HANDshake:RATE command. This setting
affects strobe width, memory clock rate, as well as the setup and hold
times. Alternatively, the reciprocal form of the command
CONFigure:DIGital:HANDshake:CTIMe can be used to specify the speed in
terms of time instead of a rate. T
CYCLE
begins when the L4450A executes
one of the input commands.
The timing should be such that the device sending the data ensures the data
lines are valid prior to T
SETUP
time. The trailing edge of the strobe line
indicates the L4450A will latch the data within the T
HOLD
time. T
SETUP
is
90ns and T
HOLD
is 0ns. Since T
HOLD
= 0ns, the sending device can use the
trailing edge of the strobe to initiate a change in the data lines.
A synchronous unbuffered input is shown in the diagram below

(default handshake line polarity).
H0 (Direction)
H1 (Strobe)
Data In
Don't-Care Valid Don't-Care
T
SETUP
T
HOLD
T
CYC LE
T
CYC LE
/ 2 T
CYC LE
/ 2
For example, the following SCPI commands set the L4450A to have a
16- bit input using synchronous handshake. Two data inputs are then
performed and the strobe line is pulsed for each query. The I/O direction
line is set high following the first
SENSe:DIGital:DATA:WORD? query and
remains high until the digital channel is reset or reconfigured.
CONF:DIG:WIDT WORD, (@1101)

CONF:DIG:DIR INP, (@1101)

CONF:DIG:HAND SYNC, (@1101)

SENS:DIG:DATA:WORD? (@1101)

SENS:DIG:DATA:WORD? (@1101)