Table of Contents
Advertisement
Prime Proprietary
Principles of Operation
NOTE
All I/O controllers, except the VCP, must have BPAPEL, BPAPER,
BPDPEL,
and
BPDPER
lines
disabled on them, due to a timing
discrepancy between the CPU and the
controller
in
reporting
this error.
The VCP is the only one with proper timing.
INPUT PARITY GENERATION AND CHECKING
The
controller
generates byte parity on each address it sends on the
BPA.
The CPU receives the parity as signals
BPALP
and
BPARP,
then
checks
it.
The
controller
also generates byte parity on each data
word it sends on the BPD.
Signals BPDLP and BPDRP carry the parity to
the CPU which checks it again.
If
the
CPU
detects
bad
parity,
a
machine check occurs, subject to the same conditions as above.
4.2.10.4 Interrupts
While the central processor is running a program, it monitors a signal
(BPCIRQ)
from the controllers in the backplane.
When the signal goes
true, the central processor
is
notified.
The
CPU
interrupts
its
present
job
to
service
the
controller.
After
servicing
the
controller, the processor returns to what it was doing.
When large amounts of data need to be transferred,
a
series
of
PIO
instructions
is
sent to the controller to set up the operation.
The
controller then supervises the operation, requesting a DMX transfer as
needed.
This frees the
processor
to
do
other
tasks,
Interrupts
inform
the
central
processor
when controller service is needed and
when an operation is completed.
The following
aspects
of
interrupts
are
discussed
in
the
next
subsections:
@
Device Driver Programs
@
Program Vectoring
@
Interrupt Modes
e
Interrupts in Process Exchange Mode
@
Memory Increment Interrupts
@
Interrupt Inhibits/Enables
@
Override Inhibits
@
Interrupt Priority Network
Highest Priority Active Interrupt
4.2.10.4.1 Device Driver Programs
Each controller can perform
a
limited
number
of
operations.
For
example,
the
disk
controller
can
seek,
read
a record or write a
record.
The line printer controller, however, can only write data
to
a printer and control the line spacing.
Each controller in the system
4
-
19
070-C
Advertisement
Table of Contents
