270 34980A User’s Guide
10 64-Bit Digital I/O Module with Memory and Counter
This command sequence set the first 8 bits (channel 101) to normal
polarity for input and output operations, set the next 8 bits (channel 102)
to inverted polarity, and then combines the bits into a 16- bit channel.
When this WORD channel is used, the first eight bits will input or output
using normal polarity but the next 8 bits will read or written using
inverted polarity.
Threshold, level, and drive settings all behave in the same manner as the
polarity setting described above.
Handshaking
Handshaking provides a means to synchronize the input or output of
digital data. By default, no handshaking is used and data is input or
output as the command is executed. The handshake is configured per
bank.
The 34950A provides a synchronous handshake mode (strobe handshake).
You can use this mode with basic input and output operations. You must
use this handshake mode to use buffered I/O (see “Buffered I/O
Operations” on page 277).
The handshake is performed using three lines on each bank. The lines are
labeled H0, H1, and H2. The function of each line is set by the input or
output mode in use. Since there are only three handshake lines per bank,
the SCPI handshake commands are only valid for the first channel in a
bank. Once handshaking is enabled, it applies to the width of the first
channel in the bank.
The three handshaking lines on each bank also differ slightly if you are
using buffered (memory) I/O (see page 277) or unbuffered I/O operations.
You can also perform unbuffered operations without any handshake.
The function of each line for each mode of operation is defined in the
table below.
H0 H1 H2
Unbuffered Synchronous
Input
I/O Direction (output) Strobe (output) Not Used (Hi-Z)
Unbuffered Synchronous
Output
I/O Direction (output) Strobe (output) Not Used (Hi-Z)
Buffered Synchronous Input Start/Stop (output) Not Used (Hi-Z) Input Strobe (input)
Buffered Synchronous Output
(internal clock)
Start/Stop (output) Strobe (output) Not Used (Hi-Z)
Buffered Synchronous Output
(external clock)
Start/Stop (output) Not Used (Hi-Z) Output Strobe
(input)
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