System Board Check - Epson PC AX Technical Manual

REV .A DIAGRAMS AND REFERENCE MATERIALS
1. System Board Check
This module checks the operation of each IC contained in the
systemboard. The checking operation is performed in the following
order,and the program displays an error message when some error is
detected.If noerror is detected, the program displays no error
message.
1. 80286 Processor check
2. 146818 CMOS shutdown byte check
3. 27256 ROM checksum check
4. 8254 Timer Counter check
5. 8237 DMA Controller check
6. SN74LS612 DMA Page resister check
7. 8237 Memory reflesh check
8. 8042 Keyboard Controller check
9. 80286 instruction check
10. 146818 CMOS checksum and battery check
11. 8259 Interrupt Controller check
12. 8254 Timer Counter speed check
13. 80286 protect mode check
When the system board check is started, the program displays
following message.
+-----------------------------------------------------------------+
I I
I I
: SYSTEM BOARD CHECK :
I I
I I
+-----------------------------------------------------------------+
The remainder of this section describes the procedures for
each checking operation.
1) 80286 Processor Check
The 80286 Processor check performs writing and reading checks
on the 80286 flags and segment registers.
a. "Offh" is stored (safh) into the 8080 flag, then re-loaded
(lahf). The flags are checked and it is considered an error
i f
any of the below flags are not set (if the flag
=
0):
CF (Carry Flag)
ZF (Zero Flag)
PF (Parity Flag)
SF (Sign Flag)
AF (Auxiliary Carry-BCD)
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