10
Agilent 34950A 64-Bit Digital I/O and Counter Module User’s Guide
Handshaking
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
CYCLE
/2 before asserting the strobe line. The leading edge of the
strobe indicates the data is valid. The strobe line is asserted for T
CYCLE
/2
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
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. The timing should be set such that the
device receiving the data can read the data lines during the T
CYCLE
/2 time.
A synchronous unbuffered output is shown in the diagram below (default
handshake line polarity).
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
SOURce:DIGital:DATA:WORD
command and
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)
H0 (Direction)
H1 (Strobe)
Data
Ou
t
I
n
v
alid
Valid
T
CYC LE
T
CYC LE
/ 2
T
CYC LE
/ 2
