Yamaha V9938 MSX-Video display processor pinout

DIP-64. MSX2 video: TMS9918A-compatible VDP with bitmap modes, 512-color palette, RGB and composite out, 64-128 KB VRAM

Runs from a 21.47727 MHz crystal on XTAL1/XTAL2 and hands the Z80 its clock on CPUCLK (crystal / 6 = 3.58 MHz), so a dead V9938 or crystal can stop the whole machine, not just the picture. Ports $98 (VRAM), $99 (registers), $9A (palette), $9B (register pointer). Up to 128 KB VRAM on /CAS0 and /CAS1 (/CASX for 64 KB expansion VRAM), with 16K x 1, 16K x 4, 64K x 1 or 64K x 4 DRAM. Linear R, G, B and composite VIDEO out on pins 21-24 through external buffers. Unlike the TMS9918A, bit 0 of each bus is the LSB (CD0, RD0, AD0). Pin spacing is 1.778 mm: an ordinary 0.1 in socket will not fit.

Open the interactive V9938 pinout

Pins

Pin	Name	Type	Signal
1	GND	ground	0 V.
2	/DHCLK	clock	Dot clock for high resolution, open drain.
3	/DLCLK	clock	Dot clock for low resolution, open drain; can be an input (multi-VDP systems).
4	/VDS	ctrl	VRAM data select: LOW when the VRAM access is for display data, HIGH for other accesses.
5	HSYNC	video	Tri-level: HIGH non-HSYNC, MIDDLE HSYNC or non-color-burst period (output); LOW = HSYNC input.
6	CSYNC	video	Tri-level: composite sync output (HIGH levels); LOW = VSYNC input. UNVERIFIED
7	BLEO	video	Tri-level open drain: HIGH secondary field active, MIDDLE first field active, LOW blanking.
8	CPUCLK	clock	Clock out = crystal / 6; on an MSX2 this is the Z80 clock.
9	/RESET	ctrl	Initializes all V9938 circuits.
10	/YS	video	Superimpose switch: HIGH = V9938 output transparent (external video shows), LOW = V9938 output opaque.
11	CBDR	ctrl	Color bus direction: HIGH input, LOW output.
12	C7	io	Color bus bit 7 (MSB); mouse YB.
13	C6	io	Color bus bit 6; mouse YA.
14	C5	io	Color bus bit 5; mouse XB.
15	C4	io	Color bus bit 4; mouse XA.
16	C3	io	Color bus bit 3: color code out, or digitize input.
17	C2	io	Color bus bit 2.
18	C1	io	Color bus bit 1.
19	C0	io	Color bus bit 0 (LSB).
20	GND DAC	ground	0 V for the video D/A converters.
21	VIDEO	video	Composite video output (needs the external buffer).
22	G	video	Linear green output.
23	R	video	Linear red output.
24	B	video	Linear blue output.
25	/INT	ctrl	Interrupt to the CPU, open drain (frame and line interrupts).
26	/LPS	io	Light pen or mouse switch input: LOW = switch on.
27	/LPD	io	Light pen detect or mouse switch input: LOW = light detected or switch on.
28	MODE 1	ctrl	CPU interface mode select bit 1 (with MODE 0 picks one of the four VDP ports; normally Z80 A1).
29	MODE 0	ctrl	CPU interface mode select bit 0 (normally Z80 A0).
30	/CSW	ctrl	CPU-to-VDP write strobe.
31	/CSR	ctrl	CPU-from-VDP read strobe.
32	CD7	data	CPU data bus bit 7 (MSB).
33	VBB	nc	Back bias (substrate) output. No connection.
34	CD6	data	CPU data bus bit 6.
35	CD5	data	CPU data bus bit 5.
36	CD4	data	CPU data bus bit 4.
37	CD3	data	CPU data bus bit 3.
38	CD2	data	CPU data bus bit 2.
39	CD1	data	CPU data bus bit 1.
40	CD0	data	CPU data bus bit 0 (LSB).
41	RD0	data	VRAM data bus bit 0 (LSB).
42	RD1	data	VRAM data bus bit 1.
43	RD2	data	VRAM data bus bit 2.
44	RD3	data	VRAM data bus bit 3.
45	RD4	data	VRAM data bus bit 4.
46	RD5	data	VRAM data bus bit 5.
47	RD6	data	VRAM data bus bit 6.
48	RD7	data	VRAM data bus bit 7 (MSB).
49	AD0	addr	VRAM multiplexed address bit 0 (LSB).
50	AD1	addr	VRAM address bit 1.
51	AD2	addr	VRAM address bit 2.
52	AD3	addr	VRAM address bit 3.
53	AD4	addr	VRAM address bit 4.
54	AD5	addr	VRAM address bit 5.
55	AD6	addr	VRAM address bit 6.
56	AD7	addr	VRAM address bit 7 (MSB).
57	R/W	ctrl	VRAM write strobe (LOW = write).
58	VCC	power	+5 V supply.
59	/CASX	ctrl	Column address strobe for expansion VRAM.
60	/CAS1	ctrl	Column address strobe, VRAM second half. UNVERIFIED
61	/CAS0	ctrl	Column address strobe, VRAM first half. UNVERIFIED
62	/RAS	ctrl	VRAM row address strobe.
63	XTAL1	clock	Crystal, or external oscillator input.
64	XTAL2	clock	Crystal (other side).

Fitted in

MSX2 (generic) Varies by maker; 64-pin shrink DIP (SDIP, 1.778 mm pitch), usually beside the VRAM

Yamaha V9938 MSX-Video display processor pinout

Pins

Fitted in

Sources