 |
|||
|
|
|||
| ||||||||||
|
|  MIL-D-81347C(AS)
2.1.4.2.1
Command Word - Computer A shall be able to transfer one 30
bit command to Computer B by following the control .line sequence below.
(1) Computer B sets the Interrupt Enable when it is ready to
accept a command word from Computer A.
(2) Computer A recognizes the Interrupt Enable as an External
Function Request and places the External Function word on the 30 data lines.
(3) Computer A sets the External Finction to indicate that the
External Function word is on the data lines.
(4) Computer B recognizes the External Function as an Inter-
rupt and accepts the command word.
(5) Computer B clears the Interrupt Enable line and sets the
Input Acknowledge line.
(6) Computer A recognizes the Input Acknowledge as a Resume
and clears the External Function line.
In the event that Computer A sets the External Function line
while the Interrupt Enable line is cleared (this is possible when an External Function with Force in-
struction is used), all communications on the associated group of output channels in A will be sus-
pended until Computer B acknowledges receipt of the External Interrupt or until an inter-computer
time out interrupt in A permits A to resolve the problem. If either Computer A or B is not designed
for External Function Requests or Interrupt Enables, then all External Functions shall be transferred
by force, and interrupts shall be transferred as shown by Method II of Figure 1-3.
2.1.4.2.2
Data Word - Computer A shall be able to transfer 30 bit words
to computer B by following the control line sequence below.
( 1 ) Computer B initiates an input buffer and Computer A initi-
ates an output buffer for the required channel.
( 2 ) Computer A places data in the data lines.
( 3 ) Computer A sets the Ready line to indicate that the data is
on the line.
( 4 ) Computer B recognizes the Ready signal as an Input Data
Request signal and, at its convenience, accepts the data word.
(5) Computer B sets the Input Acknowledge.
(6) Computer A recognizes the Input Acknowledge as a Resume
signal and clears the Ready (Input Data Request ) line.
(7) Repeat steps (2) through (6) for each word specified in the
buffer.
2.1.5
I/O Priority - The computer shall perform an 1/0 priority scan
concurrent with the performance of a program instruction sequence. The succession in which events
are processed shall be in accordance with the function priority specified in the Priority Table,
Table 1-3. For all events which are channel dependent, channel priority shall be considered first,
function priority second.
Channel priorities shall be assigned as follows:
(1) The four input/output channel groups, in order of descend-
ing priority are: 1/0 Group 3, 1/0 Group 2, 1/0 Group 1, and I/O Group 0.
331
|
|
Privacy Statement - Press Release - Copyright Information. - Contact Us |
Click
here for thousands of PDF manuals