Vi-4. Display Adapter Boards; Vi-4-1. Pin Description Of The 68B45 - Canon A-200 series Service Manual

VI-4. Display
Adapte r Boards
The A-200 is equipped with monochrome or color display adaptor board as the standard. Namely,
Model M1 and M2 have the monochrome board, and Model C1 and C2 have the color board.
Either adaptor boards are controlled by the 68B45 CRTC.
VI-4-1. Pin Description of the 68845
Vss
VSYNC
RES
HSYNC
lPSTB RAO
MAO
RAl
MA1
RA2
MA2 RA3
MA3 RA4
MA4 DO
68845
MA5 D1
(Top view)
MA6
10 D2
MA7 11
D3
MA8
D4
MAg
D5
MAlO
D6
MAll
D7
MA12
CS
MA13 RS
DISPTMG E
CUDISP R/W
Vee
ClK
Figure 6-29
• DO - 07: bi-directional data bus
These terminals are used when transferring data between the CRTC and the CPU. These out­
puts turns three state buffer.
Unless the CPU reads the contents of the register of the CRTC, this bus remains high-impedance.
• RIW (ReadIWrite)
This signal controls a direction of data transferring between the CRTC and the CPU. That is, when
this signal is HIGH, a data from the CRTC is transferred to the CPU, and when LOW, a data from
the CPU is transferred to the CRTC.
• CS (Chip Select)
Only when the CS signal is LOW, the CPU can access internal registers of the CRTC.
• RS (Register Set)
This signal is used when dividing the internal one address register and 18-control registers. That
is, when this terminal is LOW the address register is selected, and when HIGH the control registers
is selected.
• E (Enable)
This signal is used as a strobe signal when the CPU reads from or writes to the internal registers
of the CRTC.
86