IBM Series 1 User Manual page 15

The direct proqram control adapter feature card supplies a
loqical subset of the I/O channel architecture. This
feature provides a conv€nient meaDS of attaching I/O devices
and subsystems to a 4953 or 4955 Processor. The interfacE
circuits are TTL compatible. The adapter is designed to
perform direct proqram control
(DPC)
functions only; cycle
steal (overlapped) operations cannot be performed. The
feature card can be confiqured to accommodate 4, 8, or 16
I/O
device addresses. The adapter allows for interrupt
vectorinq of 16 interrupt sources.
User attachment is throuqh three top-card connectors.
There are 75 siqnal lines; these include:
18
data bus out,
18
data bus in, 16 interrupt request in. 3 function bits, 4
modifier bits, 4 device address bits, and 12 control and
response lines. The data flow is always 16 bits without.
parity option or 18 bits with parity option (2 parit.y bits).
The customer access panel feature provides an assembly for
mountinq optional, quick-disconnect type connectors for
I/O
equipment. The assembly can accommodate: one timer
connector, one teletypewriter connEctor, and up to four
connectors for either the in teqrated digital input/output
feature, or the customer direct program control feature.
The assembly mounts to the standard rack mounting screw
holes at the rear of the enclosuIE frame.
1-4 GA34-0033
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