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The CIU can be tested for a busy/not-busy condition by the DATANET-30. This busy/not-busy
test tells the DATANET-30 whether or not it can put data into the data and address registers
of the CIU-930, and whether or not it can take data from the data register.
The DATANET-30 communicates with the Compatibles/200 central processor only on a memory
interrupt basis.
The DATANET-30, under program control, puts data and address information
into the CIU to interrupt the central processor. The central processor cannot control the DATA-
NET-30, as is possible with other peripheral equipment. Since both the DATANET-30 and the
central processor have stored programs and since the DATANET-30 operates in real time.
the DATANET-30 must have control and priority between the two programs.
When the Information Processing system has data for the DATANET-30, it will set a flag in a
memory location of the central processor, which is periodically interrogated by the DATANET-30.
When the DATANET-30 is ready to accept the traffic, a control instruction is sent to the central
processor, the processing system program is interrupted, and the traffic is transmitted to the
DATANET-30.
The DATANET-30 then processes the traffic and
s~nds
it on to the designated
remote station.
Thus the information processing system and the DATANET-30 exchange control
words, instructions, and traffic under control of the DATANET-30.
THE CIU-931 COMPUTER INTERFACE UNIT
The CIU-931 Computer InterfaceUnitoftheDATANET-30is an 18-bit buffer within the DATANET-
30 that provides the connecting link between the DATANET-30 and a General Electric Compatibles/
400 system.
The CIU connects into the buffer selector of the DATANET-30 and one standard
input/output channel of a Compatibles/400 system.
The channel may be either a word channel
or a character channel for input and output. Direction of data flow is under program control.
The transfer rate is up to 43,200 characters per second or 14,400 DATANET-30 words per
second. The actual transfer rate will be determined by the DATANET-30 program.
The CIU permits both the DATANET-30 and the Compatibles/400 system to execute programs
concurrently with the transfer of data in either direction. The CIU is able to respond to the
processing system without the need of service from the DATANET-30 program. When the CIU
responds to the processing system, a signal is generated to indicate to the DATANET-30 program
that service is required.
The information from the Compatibles/ 400 command will be stored
in the CIU until the DATANET-30 program is able to service the request. Conversely, the
CIU will request service from the processing system and store the request until the latter can
respond.
All data transferred thru the CIU-931 is parity checked for accuracy. In the event of a parity
error, an appropriate signal is generated in the CIU.
[ID&u&~~u~ ~®------------
1-6
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