IBM Series 1 User Manual page 163

4.
5.
6.
When the external equipment has received the new data,
it deactivates the external sync input line (up level).
The system then deactivates the ready line and posts an
interrupt to the channel indicating that the external
equipment
has
received
the
data.
After the interrupt
has been
serviced, another write DO
command is performed to set up the group for the next
data transfer sequence. The system is then waiting for
the next transition of the external sync input to an
active state.
Dia~n2§!i£
Mode. The diagnostic mode is entered
by
performing the Disable DO and
the
Set Diagnostic External
Sync commands. These instructions disable all outputs and
inputs for the group. If the set Diagnostic External Sync
command is performed after the Disable DO command, and if
the DO group is set up to perform an "External Sync"
transfer, the Set Diagnostic External Sync command causes an
interrupt to be posted to the channel. If an interrupt is
pending, busy is returned and the commands are not
performed. In the diagnostic mode, all commands and modes
operate as usual except that the user's inputs are disabled
and the user's outputs are turned off. When leaving
diagnostic mode, the data in the DO register is placed on
the user's outputs and the user's inputs are enabled.
Figure 5-2. DO external sync timing diagram
,.
Ready
External:
sync
I
I
Interrupt I
Program control
"
Prepare
Arm
5-6 GA34-0033
Program control
"
Write DO
Service
Write DO
(;