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L4450A 64-Bit Digital I/O with Memory and Counter 8
L4400 User’s Guide 203
This command sequence sets 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 L4450A provides a synchronous strobed handshake mode. 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 210).
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 (see page 210) 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)