Texas Instruments 990 User Manual page 96

Applications Programming
2280122
BYTE 0
BYTE 2
>4D
I/O OPCODE
STATUS CODE
RESERVED
Figure 4-2 Supervisor Call Block for Requesting Activation Services
The contents of the SVC block shown in Figure 4-2 are as follows:
Byte 0 contains the opcode >4D for the SVC.
Byte 1 contains the status code returned by the SVC. The
applications program should check the sta tus code
returned and take appropriate action. The codes and
their meanings are as follows:
Code Meaning
00 Activation services has accepted the call.
01 Illegal I/O opcode.
02
Not used.
03
Invalid task ID.
activation services
assigned to it by
program NETGEN.
04 Not used.
The task requesting
must have a network ID
the network generator
05 System buffers are full; unable to accept
th e request.
06 Communications system inactive. In the
primary station, the request is not
accepted. However, in a TX5 secondary this
code is ignored and the request is accepted.
Byte
2
contains the I/O opcode supplied by the applications
program. Explanations of I/O opcodes used to make
requests of activation services are as follows:
4-10
2270526-9701