Memory Card: Revision A
Last Updated: November 09, 2005 09:48:34 PM
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Revision A of the memory card with the RAM installed at 0x0000 – 0x7FFF and the EPROM at 0x8000 – 0xFFFF. The jumper blocks on the left enable and disable 4K memory blocks. This card has RAM 0x0000 – 0x6FFF and EPROM 0x8000 – 0xEFFF areas are enabled.
Description
The memory card contains 64K of RAM and 64K of EPROM made up four 32K x 8 chips (2 RAM, 2 EPROM). The RAM and EPROM are each spread across the entire 64K address space of the 1802. Each 4K block of RAM or ROM can be separately enabled or disabled by one of four jumper blocks, each RAM and EPROM chip has a separate 8 x 3 jumper block. Of course any 4K block can only be occupied by either one of RAM or EPROM. The card was designed with this flexibility to accommodate old software of my own and new software such as ELF/OS. The card replaces the original System-4 16K Ram card.
NOTE: This was the first new card built for System-5 and although the first design and layout worked, Rev-A of the card, has a few simple flaws (no bypass capacitors) and is missing a few features and standards I decided each System-5 card should conform with.
Issues/todo log
| Date | Description | Status | |
| Dec-20-2005 | Add bypass capacitors | Done | Rev B |
| Dec-23-2005 | Update bus connector – Fix labels and hole size | Done | Rev B |
| Jan-12-2005 | Add Power and Status LEDS | Done | Rev B |
| Jan-23-2005 | Add card name and version label | Done | Rev B |
| Feb-12-2005 | Add label information to jumper block silk screen | Done | Rev B |
| Mar-05-2005 | Convert jumper blocks from separate GND and VCC for each block location to a pull up resistor and GND jumper for each block. Combine jumper selection block
for each 32K RAM/EPROM pair. |
Done | Rev B |
Schematics, board layout, and operational description
| Revision | Production Date | Schematic | Layout | Operational Description |
| A | Dec-16-04 | mem3.sch | mem3.brd | Rev. A ops notes |
| B | Current Development Board
*UNBUILT/UNTESTED* |
mem3-b.sch | mem3-b.brd | Rev. B ops notes |