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1.13.0 I/O PARITY CHECKING AND
GENERATION
Parity errors can be detected between the port
and the processing unit, or the port and an I/O
device. Normally, the port operates in odd parity.
However, some diagnostic programs use even par-
ity. See the parity checking and generating chart
below.
Unit
10l&
10S&
10Cl
10CS
Channel
PG
PC
Display
PC
PC
Keyboard
PC
PG
Belt or
Serial
Printer
PC
1
PG
1
on
Data
Transfer
33FD
PC
Only
PG
1
on
Data
Transfer
Disk
PC
Only
~SCA/SDLCI
PC
PG
PC
=
Parity checked
PG
=
Parity generated
Sense
Int lVl Cycle
Status
Steal In
No PC-
PG in
Channel PC
-
N/A
-
N/A
-
N/A
-
PG
2
-
PG
-
N/A
Note:
Attachments generate a parity bit on the
OBI when responding to a Jump I/O command
whether or not the condition true response
(CBI-4) is met.
Cycle
Steal Out
PC from
CPU PG
to DBO
N/A
N/A
N/A
N/A
PC
N/A
1
Attachment activates the CBI-4 line to the CPU, which
denotes that parity is not generated on OBI for transfers
to the channel.
233FD cycle steals on IMPL only.
System Data Flow
Processing
Unit
ALU Clocks,
Data Bus Out
Data
Busln
Kf~Y
hOdld
P,
11'''''
Disk
33FD
BSCA
or
SDLC
Modem'
or
Data
Set
ments
Other
1/0
Devices
Introduction
1-13
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