EF6805U3 Datasheet, PDF (10/31 Pages) STMicroelectronics – 8-BIT MICROCOMPUTER UNIT

EF6805U3
The A and X registers and all RAM locations except
$07F and $07E are modified.
ROM CHECKSUM SUBROUTINE - The ROM self-
check is called at location $F95. The A register
should be cleared before calling the routine. If any
error is detected, it returns with the Z bit cleared ;
Figure 11 : Self-check Connections.
otherwise Z = 1, X = 0 on return, and A is zero if the
test passes. RAM location $040 to $043 is overwrit-
ten. The checksum is the complement of the execu-
tion OR of the contents of the user ROM.
* This connection depends on clock oscillator user selectable
mask option. Use jumper if the RC mask option is selected.
LED MEANINGS
PC0 PC1 PC2 PC3
Remarks
(1 : LED ON ; 0 : LED OFF)
1 0 1 0 Bad I/O
0 0 1 0 Bad Timer
1 1 0 0 Bad RAM
0 1 0 0 Bad ROM
0 0 0 0 Bad Interrupts or Request Flag
All Flashing Good Device
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