Texas Instruments 990 User Manual page 92

Applications Programming
The I/O opcodes available to applications programs
and the functions performed are as follows:
Code Function Performed
00 Reserved - no call. Applications should not
use this code.
01 Reserved - no call. Applications should not
use this code.
02 Write/send data. Causes data pointed to by
bytes 6 and 7 to be moved to the
communications output buffer and sent to the
DID identified in bytes 14 and 15.
03 Read input data. If input data is found,
the da ta is moved from the communications
input buffer and stored beginning at the
address pointed to by bytes 6 and 7.
04 - 07 Activation services functions. (For
activation services calls, the SVC block
consists only of bytes 0 through 3; the
remainder of the call block is not required
for these calls. See paragraph 4~2.2.l)
Byte 3 is reserved.
Byte 4 contains system flags that are defined as follows:
Bit 0 Not used.
Bit 1 0= No errors occurred.
1= Error occurred on the call.
Bits 2-7 Not used.
Byte 5 contains user flags that are reserved for future
use.
Bytes 6
and 7 contain the starting address of
. applications program~s data buffer. For
operations, this is the starting address
input data is stored.
the
read
where
Bytes 8 and 9 contain the logical record length of the
applications
program~s
input buffer for read
operations. These bytes specify the maximum number
of input characters (each character is one byte)
that may be stored in the input buffer pointed to
by bytes
6
and 7.
4-6
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