Table of Contents
Advertisement
USING THE PARITY OPTION
PARITY ERROR ACTION
The action taken when a parity error occurs (when armed) is
determined by connecting a jumper wire between "PEn (near
location 3E) and one of the following labeled locations:
PINT/
NMI/
VI0/-VI7/
Causes an interrupt request in systems not using
vectored interrupts.
Causes a non-maskable interrupt request in Z80
computers.
Connecting to one of these eight locations causes a
vectored interrupt request at the corresponding
priority level.
Note: The on-board LED lights whenever a parity error is
detected, whether armed or not.
PARITY ERROR ARMING
The parity error logic is disarmed at power-on and reset.
The
parity error logic can be armed or disarmed under program control
by loading a control value into the A-register and executing an
OUT 0C0H instruction.
Bit 0 of the control value should be 1 to
arm the parity logic and 0 to disarm it.
Configuration of the
DIP header at location 7D will determine which bit (of bits 1-7)
in the control valUe, if 1, will cause arming or disarming of the
parity logic for the RAM-16-A.
(Arming or disarming the parity
error logic also resets the parity error "flip-flop.)
Parity Select Bit
Header Connection
Bit 1
pin 4 to pin 14
Bit 2
pin 4 to pin 11
Bit 3
pin 4 to pin
9
Bit 4
pin
4
to pin 12
Bit 5
pin 4 to pin 10
Bit 6
pin 4 to pin
8 (standard)
Bit 7
pin 4 to pin 13
Note that the standard HORIZON convention is to use bit 6 for all
RAM-16-A boards in the computer.
Using this convention, the
following two instructions will reset then arm the parity logic
for all the RAM boards:
MVI A,41H
OUT 0C0H
and the following two instructions will reset and disarm the
North Star 16K RAM Board
24
Advertisement
Table of Contents
