Canon AS-100C, Field Service Manual

Page: 13 / 136

I SYSTEM BÜSl
A system bus is used for 16-bit processor 8088 to control the entire
system. The system bus consists of a 20-bit address bus with 1 MB
address space,
8
-bit data bus, and a control bus for read/write
control and system bus controlled by a microprogram.
The memory area appropriated for 8088 processor is divided into
two as shown in Fig. 1.2.3; One is the system memory area and the
other is I/O memory area.
This memory area division is performed automatically within the same
address area of 20 bits - 1 MB by a microprogram.
00000
H
0000H
System
memory
area
I/O memory
area (64 KB)
(1 MB)
FFFFH
FFFFFH
ROM
RAM
Hardware memory area for I/O
controller
Example: Hardware address
for DMA and FDD controller.
VRAM in DISPLAY-
CONT
Fig. 1.2.3
1-7