Standard Device Byte - RCA 70/46 Reference Manual

Channel Status Byte
(Cont'd)
Standard Device Byte
Input/OutPut Operation
4. Invalid Key. The memory protection key in the Channel Address
Word is not zero and the system does not have the Memory Protect
option installed.
Notes:
1. If a program check error occurs during input/output initiation,
the operation is suppressed and the program is notified of the error
by the condition error setting.
2. If a program check error occurs while the input/output operation
is in progress, the operation is terminated and a channel interrupt
occurs for the specified channel.
3. If a program check error occurs during chaining (command or
data), a channel interrupt occurs for the specified channel and
chaining is suppressed.
Bit Position
11
is the protection check bit. When set, this bit indicates
that the channel tried to store data in a protected main memory area. The
operation is terminated and a channel interrupt occurs for the specified
channel. If chaining (command or data) is in progress, it is suppressed.
Bit Position
12
is the channel data check bit. When set, this bit indi-
cates that a parity error was detected in the channel, in main memory,
noOn-addressable main memory or in scratch-pad memory. Characters with
bad parity going into memory are replaced with the systems error byte
(hexadecimal FF), and the input/output operation is completed. For parity
error characters going to a device, (writing) the invalid character is
transferred unchanged, the operation is terminated and a channel interrupt
occurs for the specified channel. (The transfer of sense byte (s) to memory
is not checked for parity.)
Bit Position 13 is the channel control check bit. When set, this bit
indicates that a machine 'malfunction has occurred affecting the channel
controls. Conditions which cause this bit to be set are parity error in the
Channel Command Word, data address, or contents of the Channel Com-
mand Word. The operation is terminated and a channel interrupt occurs
for the specified channel. If chaining (command or data) is in progress,
it is suppressed.
Bit Position 14 is reserved for use by the processor.
Bit Position
15
is the termination interrupt bit. When set, this bit
indicates that a termination interrupt has been effected.
Important: The channel status byte is reset only when an input/output
operation is initiated .
• The standard device byte is stored in scratch-pad memory in the
Assembly/Status register (bit positions 24 through 31) for the appropriate
channel. This byte indicates the status of a device after an input/output
operation. It may also indicate a device request interrupt.
The standard device byte is automatically stored when:
1.
An input/output interrupt is serviced (request or termination).
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