TM 11-6625-3081-23
1-21. ELECTRONIC STATION (cont)
1-21
i.1.
DIGITAL COMPUTER ASSEMBLY 1A11
(1) General.
Digital computer assembly 1A11 (FO-1O.1) consists of a backplane,
power supply the following CCAs:
Control store A1
Sequencer A2
Data path A3
Cache control A4
Memory controller A5
Memory A6
HP-IB interface A7/A11
Asynchronous serial interface A8
IEEE interface A9
Priority jumper A1O
Parallel interface A12
Buffer interface A13
(a) The backplane is a multilayered printed circuit card which contains
plug-in connectors for CCAs and power supply.
It provides the electrical interfaces
required for power distribution, address bus, data bus, and control lines.
Each I/0
interface CCA contains circuitry to standardize the I/0 interface to the backplane.
(b) The power Supply is contained on a single CCA which plugs into the
backplane.
It supplies +5 vdc, +12 vdc, and -12 vdc.
Power is distributed by the
backplane interface to all CCAs.
(2) Input/Output Function.
The I/0 function allows data transfer between the
computer and external devices.
Data can be transferred under CPU control or directly
into or out-of memory.
(a) Direct memory access (DMA) allows data transfer directly into or out-of
memory by passing the CPU.
Each I/0 interface CCA contains circuitry for direct
memory accessing.
Once DMA is initialized, the complete routine is handled by the I/0
interface CCA.
This transfer routine occurs as follows:
To memory:
(1) between external device and its I/0 interface CCA, and
(2) between I/0 interface CCA and memory via the backplane
data bus.
To external device:
(1) between memory and I/0 interface device via the
backplane data bus, and
(2) between I/0 interface CCA and external device.
(b) A CPU or programed I/0 transfer allows the CPU to manipulate data
during the transfer process.
Transfer of data to and from memory is the same as that
discussed during a DMA transfer.
The difference is that all data is under CPU
control.
This transfer takes a little longer.
DMA transfer is quicker and especially
useful with high-speed devices.
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