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carriage or to return the carriage can be overlapped
with other input or output operations.
As mentioned earlier, because of the design of the
SIOC
channel and the fast internal speed of the 1620,
the operation of many Process Operator Units could
be virtually simultaneous.
Interrupt Operation
The interrupt feature associated with the Process Oper-
ation Units allows the 1710 Control System to make
efficient use of various Process Operator Units and to
eliminate any waiting by the 1620 and
TAS
for an input
or output cycle to be completed. The Any
SIOC
inter-
rupt is connected to indicator 45 and can be tested with
a Branch Indicator or Branch No Indicator instruc-
tion.
The Any
SIOC
Interrupt indicator is turned on by the
SIOC
Output Error indicator, the Data Ready indicator
or any of the Unit Response indicators when the
SIOC
becomes not busy. All
SIOC
interrupts of the mainline
program are initiated only by the Any
SIOC
interrupt.
When in response status (that is, waiting and ready
to transmit or accept a character) each Process Oper-
ator Unit automatically initiates an interrupt (if
SIOC
is not busy) to signal the 1620
CPU
that it is ready to
send or accept additional data. The manner in which
each unit is placed in response status was described in
the section concerning that particular unit. Response
status is removed by the transmission of the last charac-
ter of a field or an end-of-message code.
The Unit Response indicator of the originating unit
Table 5.
slOe
Branch Indicators
Code
Q8-Qll
Indicator
also turns on. The Unit Response indicator is identified
by a 60 in
Qs - Q9
and the unit response code for the
particular unit in
QI0 - Q11.
The program can establish
an interrupt priority for input/output units by the
sequence in which the Unit Response indicators are
tested in the program.
In some programs, the user may desire to inhibit
SIOC
interrupts in certain portions of the program. To
inhibit
SIOC
interrupts, that is, to selectively mask, the
program should test the Any
SIOC
indicator with a
Branch Indicator or Branch No Indicator instruction
and then omit any read or write instructions (SLIC,
RNIC, RAIC, WNOC, WAOC) following the test. No
more
SIOC
interrupts will occur until the program exe-
cutes an
SIOC
read or write instruction (this could be
a pseudo instruction), thus freeing the
SIOC
interrupt
to operate again.
Data Ready interrupts must be serviced prior to Unit
Response interrupts, since the data to be read is occupy-
ing
IODR.
All
SIOC
interrupt signals are monitored by the
SIOC
to ensure that it is free to handle the transmission.
When the
SIOC
channel is available, the
SIOC
Not Busy
indicator is turned on and any interrupt signals from
the units are allowed to interrupt the program.
SIOC
interrupts that occur during an
SIOC
busy condi-
tion must wait until
SIOC
is not busy before interrupt-
ing the computer.
The functions of all
SIOC
Branch indicators are
shown in Table 5.
Turned on by
Turned off by
45xx
Any SIOC
6043, 6044, and 6070 through 6089 providing SIOC Not Busy (6046) is on
Program test
6040
Output Record Mark
Record mark transmitted to IODR by write instruction
Program test
6041
End of Message
Control code Record Mark transmitted to IODR by write instruction
Program test
6042
Mode Shift
Control code
2 sent to IODR by write instruction
Program test
6043
SIOC Output Error
*
Parity error detected by output unit
Program test
6044
Data Ready
*
Character sent to IODR from input unit by read instruction
Program test
6045
Alert
SIOC indicator
6040,6041,6042,6043, or 6044
Indicators off
6046
SIOC Not Busy
SIOC free to accept instruction or interrupt
SIOC busy
6070
Unit Response
*
SIOC unit ready to transmit or receive data.
(QIO..o 11 identifies individual
Not ready
to
unit:
70, No. 00; 71, No. 01; ••• 89, No. 19.)
6089
'" Interrupts
39
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