PSI BOX PLUS+ Reference
Control Functions
READ.
Receive One Byte From Addressed Talker.
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Purpose.
To receive one byte of data from the currently
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addressed talker.
The READ command is used to receive data from the
currently addressed talker one byte at a time. The data byte is
returned in the IEEE control status string at bytes 66-68. The
READ command must be used as one command in a series that
explicitly addressed devices to talk and listen.
The READ command can be used time and again to retrieve a
whole string of data however this is a tedious method, a much
easier solution is the ENTER command.
The PSI BOX drops ATN false, if not already so, at the
start of the data input sequence ATN is left false until further
instructions makes the PSI BOX become the active controller.
Format.
READ
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Params.
None.
_________
Returns.
Byte 66-68 in control status string contains the
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decimal value of the byte read.
Example.
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_
BUS MLA TALK 4 READ UNT
Bytes 66-68 in status string hold the data.
Bus Activity.
___________
_
assert ATN if not already so
LISTEN address of the PSI BOX
TAD 4 command this device to send data
DAB XXX the byte of data
UNT tell device to stop talking
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Chapter 8
