Agilent Technologies 34980A User Manual page 285

10
64-Bit Digital I/O Module with Memory and Counter
Synchronous Unbuffered Outputs For synchronous handshake unbuffered
outputs, the H0 line indicates the direction of the transfer. This line is set
low to indicate an output operation. The H0 line will remain in the low
state until the 34950A direction is changed. The H1 line is the strobe
output line.
When the 34950A executes an output command, it sets the data lines and
waits for T /2 before asserting the strobe line. The leading edge of the
CYCLE
strobe indicates the data is valid. The strobe line is asserted for T /2
CYCLE
and then de- asserted. The H2 line is not used and is set to high
impedance.
The timing of the output operation is controlled by the T parameter
CYCLE
set using the command. This setting
CONFigure:DIGital:HANDshake:RATE
affects strobe width, memory clock rate, as well as the setup and hold
times. Alternatively, the reciprocal form of the command
can be used to specify the speed in
CONFigure:DIGital:HANDshake:CTIMe
terms of time instead of a rate. The timing should be set such that the
device receiving the data can read the data lines during the T /2 time.
CYCLE
A synchronous unbuffered output is shown in the diagram below (default
handshake line polarity).
H0 (Direction)
Data Out
Invalid Valid
T
CYC LE
T / 2 T / 2
CYC LE CYC LE
H1 (Strobe)
For example, the following SCPI commands set a 34950A in slot 5 to have
a 16- bit output using synchronous handshake. Two data outputs are then
performed and the strobe line is pulsed for each. The I/O direction line is
set low following the first command and
SOURce:DIGital:DATA:WORD
remains low until the digital channel is reset of reconfigured.
CONF:DIG:WIDT WORD, (@5101)
CONF:DIG:DIR OUTP, (@5101)
CONF:DIG:HAND SYNC, (@5101)
SOUR:DIG:DATA:WORD #hFFFF, (@5101)
SOUR:DIG:DATA:WORD #h4DB5, (@5101)
34980A User's Guide 273