Ram Chip Location Vs. Memory Address - Omron 8025G Maintenance Manual

THEORY OF OPERATION SECTION 4
Table
4-4.
RAM chip location vs. memory address.
RAM CHIP COORDINATES
MEMORY ADDRESS
BIT POSITIONS (in octal)
27 2 6 2 5 24 2 3 22 21
2°
C8 C7 C6 CS C4 C3 C2 C1 34000 - 35777
08 07 06 05 04 03 02 01 36000 - 37777
4.4.7 Refresh Buffer Card
The refresh buffer card provides refresh data for the video display, tem-
porarily stores video status and keyboard indicator light (LED) data, and decodes
a beep signal.
Block Diagram Analysis. A simplified block diagram of the card is shown
in Figure 4-16.
Video status data is stored at address 377718 in the refresh memory. When
called from memory, at the end of each page, the data_is placed on RMO-3 in order
to update the video status latch. The BLANK and CSO-3 outputs control block and
underline cursor, video on-off, and control character blanking.
RMO·7
LED
LATCH
rr
RMO
-
3
VIDEO
N
STATUS
LATCH
IiI.
FAo~:1
RM
GATE
A DATA BUS
ICCll( :
MA9·1)
~
110
aEEP
DECOOEIi
'1
LOADLSB
,
LOADMSB
~BCANK
~CSO-:j
f
HALF
---.
LINE
GAn
~BEEP
I
BUFFER
~<om~"
CONTI'lOl
..
LOGIC
DISABLE
. - C[5·7
+
SR COUNT
_4__EOR
CLOCI<
I
_4__82
+
,-H~
CLOCK
2
. - H 8
....-POSTIME
1
~
NEXT I'lEFRESH
ROW SHIFT
-.
SHIFT
REGISnl'l REGISTER
t
EOR
Figure 4-16. Refresh buffer card block diagram.
4-48
CONTPOL IN
CONTROL OUT
CGO·7