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

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-