Vi-2-4. Memory Map - Canon A-200 series Service Manual

VI-2-4. Memory Map
Figure 6-7 shows the memory map for the A-200.
The CPU can access in maximum of 1M bytes of memory area directly. In the A-200, memory
area is constructed by ROM, system RAM, V-RAM and optional RAM. As for the optional RAM,
this figure illustrates only the 256K-byte optianal RAM board supplied by Canan. The tatal
RAM area supplied by Canan is 512K bytes (00000 to. 7FFFF). However, If all af DIP switches
(bit 1 thraugh 4 of the DIP switch 81) are set to OFF pasitian, the saftware autamatically sear ­
ches the actual amaunt af RAM installed, and adjust usable RAM area to. that amaunt. The
saftware supparts in maximum af 640K bytes RAM.
Basically, the A-200 has 16-bit data bus line and therefore, phYSical memory chip assignment
is divided into. even addresses and odd addresses. As for the RAM, a parity bit is added to either
one byte of even or odd address.
Since the A-200 uses the 4864 type dynamic RAMs, everyone chip correspands to every ane
bit af data bus.
V-RAM used in the color board is 48416 type dynamic RAMs. Everyone RAM chip is assigned
with every 4 bits of the data bus.
As for the monochrome board, it uses 6116 type static RAMs as V-RAM. Everyone chip of RAMs
corresponds to one byte of even addresses and add addresses respectively.
Carrespondence to the data bus in ROM is similar to the RAMs in the monochrome bo.ard since
2764 type P-ROM or C-MOS masked ROM is used as ROM.
FFFFE FFFFF
FCOOO
L£-
Rt::J
~ --.
EOOOO coooo
V·RAM(Color)
/-
-
U21 U20
U23 U22
COOOO
BOO
00
AOOOO
Upper
Bl000
limit of RAM
area
V·RAM(Mono.)
U43 U40
80000,
80001
!
I
OPTIONAL RAM
BOARD
60000
60001
I
I
I
40000
40001
!
O)o:tmLO .... (ON OOMCO-.:tOLO .....
.,.
M M N N N - . . - C O ( " ) M N N N .......... ,.....M
::0 ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~
I
20000 RAM
20001
00004
00005
r
r"Nr---MO)'I:f'O e,o ..... CONCOM
M M N N ..... ..... ..... CD M M N N .... .....
0)
~
.....
00002
00003
1::0 ::0 ::0 ::0 ::0 ::0 ::0 ::0.::0 ::0 ::0 ::0 ::0 ::0 ::0 ::0 ::0
IS
00000
00001
P 00 1 2 3 4 5 6 7 8 9 1011 12 13 1415 P
Figure 6-7
53