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New Rev 4 Board |
A newer version (Rev 4) of
this circuit board is available. Rev 4 includes a faster CPU,
more memory, more I/O and an optional LCD. We recommend you use
Rev 4 for new projects. Even though this older board is no longer
available, we are keeping these old pages on-line for reference
to assist people who purchased or build the older version.
Schematic Drawing
This is the complete schematic for the development board. Address and Data bus
wires are drawn separately (not in a bus), so that it's easy to color over them on a printout,
if you choose to manually connect the wires. It really is easier to
buy a bare circuit board, though.
This design and its schematic have been placed in the public domain. They are distributed in the hope that they
will be useful, but are provided without any warranty, not even a warranty of merchantability
or fitness for a particular purpose.
Also, the original (ugly) schematic that Forrest used to
create the circuit board is available for download, as a
postscript file, or a
bitmap image.
Parts List
| Quantity | Reference | Part |
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| 2 | C1,C2 | 33pf |
| 5 | C3,C4,C5,C6,C7 | >1uf, 16V (for the MAX232) |
| 1 | C8 | 100uf (>6.3 Volt) |
| 1 | C9 | 100uf (>16 Volt) |
| 3 | C10,C11,C12 | 0.1uF (Decoupling Caps) |
| 1 | D1 | 13V Zener, Digi-Key # 1N4743ACT |
| 1 | D2 | 5.6V Zener, Digi-Key # 1N4734ACT |
| 2 | D3,D12 | 1N4001 Rectifier Diode |
| 8 | D4,D5,D6,D7,D8,D9,D10,D11 | LED, Digi-Key Part # P437 |
| 1 | R1 | 1MEG |
| 1 | R2 | 1K |
| 3 | R4,R5,R6 | 10K |
| 8 | R7,R8,R9,R10,R11,R12,R13,R14 | 470 Ohm |
| 1 | U1 | 87C51 (or equiv) |
| 1 | U2 | 74HC373 (Octal Latch) |
| 1 | U3 | 6264 (8K x 8 SRAM) |
| 1 | U4 | AM28F256 (Flash ROM) |
| 1 | U5 | 82C55 (I/O Chip) |
| 1 | U6 | 74HC138 (3:8 Decoder) |
| 2 | U7,U8 | 74C00 |
| 1 | U9 | MAX232 |
| 1 | Y1 | 11.0592 MHz Xtal |
| 2 | P1, P2 | DB-9 Female Connector, Digi-Key Part # A2100 |
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Download Website
Development Board
Software
