Computer Interface Unit (Ciu 930); Data Transfer - GE DATANET-30 System Manual

Characters received by the CIU from the external computer are assembled into a three-character
word. The first character is transferred to the most significant part of the DATANET-30 word
and the third character is transferred as the least significant.
If
an End Data Transfer signal is received from the external computer before a full three-
character word is shifted into the CIU, the characters in the data register are shifted to the most
significant positions. Zeros are inserted by the CIU into the unfilled character positions before
the word is tranferred to the DATANET-30.
COMPUTER INTERFACE UNIT (CIU 930)
The Computer Interface Unit (CIU 930) provides the means for connecting a DATANET-30 and a
General Electric 215/225/235 Computer. The Computer Interface Unit occupies one module of
the DATANET-30. DATANET-30 must be within the standard distance of 50 feet from the com-
puter. The DATANET-30 would be considered the same as another controller to the GE-200
Series computer as far as memory interrupt of the computer is concerned. However, the GE-200
Series computer cannot interrupt or access the DATANET-30 as is done with other controllers.
,..
DATANET-30
~~+--21
___..4
~
~,
~~
,
,
ADDRESS
DATA
REGISTER REGISTER
~~
.4
~
~
~+---21 ---+~,
....
.....
GE-215 GE-225 GE-235
~
Figure 24. CIU 930 Connecting a DATANET-30 And a GE-200 Series Computer
Data Transfer
The CIU transfer 21-bit words between the DATANET-30 and the computer. The word is trans-
ferred in parallel. The memory address is also transferred in parallel from the address register
to the GE-200 Series computer prior to data transfer. At the DATANET-30, the 21-bit word
consists of an 18-bit word from memory, plus 1 parity bit and two control bits generated by the
DATANET-30 circuitry. At the GE-215, 225, or 235 computer, this 21-bit word represents a
20-bit word plus memory parity.
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