Racal Instruments 1260-14C Manual page 45

Module Specific Syntax 3-22
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Care should be used not to change the width when
writing to a synchronous port if the port has already
had its width defined and data loaded into the buffer.
In this case, the user should not specify a width, and
should format the WRITE data in the same size that
the synchronous port was defined at. Failure to do
so will cause the port to change its width
designation, and will clear the data in the buffer.
As soon as the command is received, an immediate write to the
specified ports occurs. A port may be written to when tri-stated,
but the value will not become present on the port until after it is
write-enabled. The data is written one data item per port, and the
number of ports must match the number of data items. The first
data item corresponds to the lowest significant port and the last
data item corresponds to the highest significant port.
Example 1:
Assume that ports 5-11 are defined as asynchronous and the user
sends the following command:
WR 1.5-7,Y,23,0,127
At the end of command execution, port 5 would be actively driving
a 23, port 6 would be driving 0 and port 7 would be driving 127.
Write operations may be performed as either a bit, byte or word-
wide operation. If no width is specified, it remains unchanged from
its previous setting, and the data must be specified in the same
form as used in the most recent WRITE or SETUP WR statement
for each port. If no width has ever been specified, the default is
byte-wide. Bit, byte and word-wide operations cannot be mixed in
a port. Only one width is active at a time and is specified as
follows.
A "Y" causes a byte-wide (8 bit) write to the ports. When writing to
a synchronous port that was previously defined or written to using
a word width, the data buffer associated with the companion port
will be cleared and the port will be disabled in future synchronous
operations until it is redefined. When a port is first defined as
synchronous or asynchronous, it defaults to byte-wide operations,
so it is only necessary to specify the byte width if the user is
changing from a different width, or wishes to clear the
synchronous write buffer. See Example 1 above for a sample of a
User Manual 1260-14C
NOTE