Canon A-200 series Service Manual page 139

®
V-RAM failure
The read data and written data don't match in the V-RAM area. The patterns of the data are "AA,
55, 00 and FF':
To determine the error bit, run the CRT check in the diagnostic program.
®-1. Monochrome Board
*
If the error bit is in even address, the displayed character may be different and if the error bit
is in odd address the displayed attribution may be different.
Replace the V-RAM chip in accordance with the following figure.
7 6 5 4 3 2
o
Character Code (Even Address)
~------- U43--------~
I
I
Bli RIG I
U40
B II
I
I RIG I B
I
Attribute Code (Odd Address)
~-- Foreground
---r-T
Intensity
' - - - - - - - - - - - - - - Background
T
Blink
Figure 8-6
®
-2. Color Board
* Check for lower 4K-byte of V-RAM
Using the 80 x 25 characters text mode, determine the error bit. If the error bit is in even address,
the displayed character may be different and if the error bit is in odd address, the displayed attri­
bution or color may be different.
7 6 5 4 3 2 0
I I
I
I I
I
I I
I
Character Code (Even Address)
L - U20.--JL- U21----1
. - U22
n
U23----,
I
Bl I RIG I B I I I RIG I B
I
Attribute Code (Odd Address)
~--- Foreground
---,--1
T Intensity
L -_ _ _ _ _ _ _ _
Background
Blink
Figure 8-7
136