Programming instructions

(b) Transfers data from the information buffer of an input device to
the AC, through the Information Collector
(c) Transfers information from the AC, through the information Dis-
tributor to the buffer of an output device
(d) Senses the flag(s) associated with a device to determine its avail-
ability
(e) Resets the flags. These commands dismiss a device without asking
for additional action.
The flags referred to above are signals generated by an external device
upon completion of its assigned task. This technique allows the Internal
Processor to resume its arithmetic operations after issuing an instruction
to a relatively slow input-output device (data rate of less than 20,000
words per second). When a flag is set to 1 by the device, it signifies that:
(a) an output action (punch out, etc.) has been completed; the Arith-
metic and Control Element may transmit data to the device.
(b) an input action (card or tape input, etc.) has occurred; information
is available for the Arithmetic and Control Element.
(c) an alarm condition exists.
Flags may be sensed, and a program skip take place, using the Output
Skip Facility (see below). Flags may be read into the AC using the iors (in-out
read status) instruction. Most flags are connected to the Program Interrupt
(see below).
The Device Selector selects an input-output device or subdevice according
to the address code of the device in bits 4-13 in the iot instruction. It then
generates IO pulses at event times 0, 1, and 2 if the appropriate micro-
instruction code bits are present in bits 17, 16, and 15. Pulse iot 0 occurs
near the end of an iot instruction, followed by iot 1 in 2 microseconds.
Pulse iot 2 occurs at the beginning of the next instruction, 1.2 microseconds
after iot 1. This timing enables one iot instruction to perform multiple
operations.
INFORMATION COLLECTOR (IC)
The Information Collector enables information to be collected from eight
l&bit word input devices. The AC must contain 0 at the time the inputs are
sampled. A word can be broken into smaller words according to the word
size requirements of the input device. The program steps for reading the
contents of a group of static parallel data bits are:
cla Clear the AC (AC must equal 0)
iot Selected device (sample the selected device outputs)
dac Y Deposit C(AC). The C(AC) are sent to a particular memory cell, Y.
(the first two steps may be microprogrammed together in one in-
struction)
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