What is it?
This is a Printed Circuit board for a
32 row by 64 character VDU. It is designed for 2k x 8 of Sram and a 2k x
8 EPROM for a character generator.
Why did you make it?
I have built many 65C02 projects and
wanted a generic VDU I could attach easily. This PCB, when populated,
will attach to any 65C02 SBC as the Databus is buffered and the address
location can be decoded as any 2k in the 64K window,
What makes it special?
You cannot buy this interface elsewhere so
I had to research and design a PCB I could use.
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| Screenshot of CEGMON dumped to
VDU Memory |
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BOM for 32 X 64 char
2kB Ram VDU PCB |
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IC1 |
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74LS245 |
Octal Bus Transceiver. |
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IC2,IC3,IC4 |
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74LS157 |
Quad 2 to 1 Data Selector. |
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IC5,IC6,IC7 |
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74LS393 |
Dual 4 bit binary counter. |
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IC8 |
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74LS139 |
Dual 2 line to 4 line decoder. |
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IC9,IC10 |
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74123 |
Dual retriggerable monostable multivibrator. (I've had feedback that 74HCT123 performs better). |
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IC11 |
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74LS165 |
8-bit parallel-load serial-out Shift Register. |
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IC12 |
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2716 |
2K x 8 Eprom or equivalent. Download chargen txt file here or Binary file here |
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IC13,IC14 |
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74LS02 |
Quad 2-Input NOR Gate. |
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IC15 |
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74LS04 |
Hex Inverter. |
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IC16 |
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74LS08 |
Quad 2 input AND Gates. |
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IC17 |
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74LS00 |
Quad 2 input NAND Gates. |
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IC18 |
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5516 |
2K x 8 Sram or equivalent. |
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C1 |
0.22uF |
(224) |
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C2 |
0.022uF |
(223) |
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C3 |
120pF |
(121) |
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C4 |
220pF |
(221) |
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C5,C6,C7,C8 |
0.1uF |
(104) |
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C9 |
1000pF |
(102) |
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C10 |
680pF |
(681) |
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C11,C12,C13,C14 |
0.1uF |
(104) |
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C15,C16,C17,C18 |
0.1uF |
(104) |
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R1 |
4.7k |
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R2 |
22k |
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R3 |
390 |
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R4 |
220 |
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R5 |
150 |
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R6 |
620 |
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R7 |
47k VR |
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R8 |
680 |
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R9 |
33k |
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R10 |
N/A |
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R11 |
4.7k |
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R12 |
15k |
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D1 |
IN4148 |
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OG1 |
12MhZ Oscillator (14 pin size) |
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J1&J2 |
2x18 way 90 degree pins |
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J3 |
8 x 2 pin |
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J4 |
RCA Connector |
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J5 |
3 way A15 selector |
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PCB Layout |
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VDU Address Decoding |
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1 & 2 |
3 & 4 |
5 & 6 |
7 & 8 |
9 & 10 |
11 & 12 |
13 & 14 |
15 & 16 |
A15 STRAPPED |
/A15 STRAPPED |
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Yes |
No |
No |
No |
Yes |
No |
No |
No |
$0000-$07FF |
$8000-$87FF |
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Yes |
No |
No |
No |
No |
Yes |
No |
No |
$0800-$0FFF |
$8800-$8FFF |
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Yes |
No |
No |
No |
No |
No |
Yes |
No |
$1000-$17FF |
$9000-$97FF |
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Yes |
No |
No |
No |
No |
No |
No |
YES |
$1800-$1FFF |
$9800-$9FFF |
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No |
Yes |
No |
No |
Yes |
No |
No |
No |
$2000-$27FF |
$A000-$A7FF |
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No |
Yes |
No |
No |
No |
Yes |
No |
No |
$2800-$2FFF |
$A800-$AFFF |
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No |
Yes |
No |
No |
No |
No |
Yes |
No |
$3000-$37FF |
$B000-$B7FF |
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No |
Yes |
No |
No |
No |
No |
No |
YES |
$3800-$3FFF |
$B800-$BFFF |
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No |
No |
Yes |
No |
Yes |
No |
No |
No |
$4000-$47FF |
$C000-$C7FF |
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No |
No |
Yes |
No |
No |
Yes |
No |
No |
$4800-$4FFF |
$C800-$CFFF |
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No |
No |
Yes |
No |
No |
No |
Yes |
No |
$5000-$57FF |
$D000-$D7FF |
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No |
No |
Yes |
No |
No |
No |
No |
YES |
$5800-$5FFF |
$D800-$DFFF |
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No |
No |
No |
Yes |
Yes |
No |
No |
No |
$6000-$67FF |
$E000-$E7FF |
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No |
No |
No |
Yes |
No |
Yes |
No |
No |
$6800-$6FFF |
$E800-$EFFF |
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No |
No |
No |
Yes |
No |
No |
Yes |
No |
$7000-$77FF |
$F000-$F7FF |
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No |
No |
No |
Yes |
No |
No |
No |
YES |
$7800-$7FFF |
$F800-$FFFF |
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Resistor Location and Values |
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CCT Diagram |
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| (c)
2021,2022,2023
Paul Bartlett |