MZ3500

4)Graphic VRAM memory (MZIR03)

• Block Diagram

1.read/write Mode

The select signal RASA, RASB and RASC are generate from RAS, A14 and A1 5 which is signal of GDC-2.

The address is allocated to each area selected by above signal.

Read/write by Z-80 via the GDC

(1) 640 x 200 dots display mode

Low High byte byte

Option I

#BFFF

1

(48K byte)

 

 

8bit structure

 

G

+8000

#4000

A

B R 16K

#0000i

R ASA ^ RAS • A14 • A15

0000 ~ 3FFF

RASB~ RAS • A14 • AlS

... 4000 - 7FFF

RASC =• RAS • A14 • A15

8000 ~ BFFF

2.Display mode

A14 and A15 are not valid and RASA, RASB, RASC are selected together. By the DBIN signal from GDC-2. 08/16 signal isgener- ated by CSP-2.

The signal of 08/16 select, after P-5 conversion for RAMA, RAMB output signal then output to VB by serial signal, or sprit the signal to VB and VR.

(08/16 select: 08 for 200 rasters. 16 for 400 rasters)

During displaying

B/W: 3 frames

Color: 1 frame

#3FFF

16K

# 0 0 0 0

8bit 8bit 31,L

 

8bit

8bit

 

 

 

Option I I

#BFFF

 

 

B/W:

6 frames

(96K byte)

 

 

 

Color: 2 frames

16bit structure

 

 

 

 

 

 

 

 

 

#8000

 

 

 

 

 

 

 

#3FFF

 

 

 

#4000

 

 

 

16K

 

 

 

#0000

1

1

 

 

16K

I

 

 

 

 

 

 

*0000

 

i f i t . i t

 

 

16bit- 32-

Page 29
Image 29
Sharp MZ-3500 service manual 8bit, Read/write by Z-80 via the GDC 640 x 200 dots display mode