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CONTROL
ELECTRONICS
Buffer Scan
CCM
• The Control Electronics logic executes processor commands by ex-
changing the required signals with the buffers to effect a bit- serial data
transfer across the CCM-Buffer interface.
Character assembly and
serializing are performed in the Control Electronics along with other
logical operations required to execute the processor commands and
generate the necessary terminations and interrupts to the processor.
A core memory within the CCM provides storage for data being
transferred among the processor, buffers, and character accumulation/
distribution areas, as well as counters and indicators. This memory has
a read-regenerate, clear-write cycle time of 2 microseconds per word
and contains 512 words, each word consisting of 18 bits including parity.
The Control Electronics supplies the pulses to the buffer which con-
trol the required bit timing or modulation rates for the communication
lines.
The modulation rates, which can be provided through oscillator
sets for various applications, are as follows:
Osci Ilator
Modulation Rates
Set
Frequency
(bits per second)
1
76.8KC
2400, 1200, 600, 300, 150, 75
64
0
0KC
2000, 250
2
57
0
6KC
1800
33.6KC
1050
3
4.27KC
134.4
5.82KC
45.5
4
3.64KC
56.9
3.52KC
110
*5
57.6KC
1800
30.72KC
960
*Set 5 is not supplied except when specifically required. Its use
necessitates the removal of either set 2 or set 3.
• The total system capability provided by a Spectra 70 Communication
System is a function of the variety of remote terminals employed, the
types of communication lines which are utilized, and the transmission rates
which must be maintained.
The transfer of data and control signals to
and from the buffers is accomplished by means of a CCM line scan. This
function scans the first 16 buffers in any CCM at a higher priority rate
than the remaining buffers attached to that CCM. All communication
lines, buffers, and device addresses can be considered to be assigned
within a high-speed group or a low-speed group. The first 16 lines are
considered the high- speed group and lines 17 through 32 or 48 are con-
sidered the low-speed group. In the 70/668-11 all 16 lines are scanned at
the high- speed rate, but this does not restrict low- speed circuits and
1-3
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