Memory Card: Revision B

Last Updated: November 09, 2005 09:48:34 PM

Not Yet Produced

Revision B not yet produced of the memory card with the RAM installed at 0x0000 – 0x7FFF and the EPROM at 0x8000 – 0xFFFF. ( FIX test with new PCB and picture) 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. (FIX ADD JUMPER DESCRIPTION). 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.

Issues/todo log

Date Description Status

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

Memory Card: Revision A

Memory Card: Revision A

Last Updated: November 09, 2005 09:48:34 PM

http://cottageworker.com/wp-content/uploads/2014/05/

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

http://cottageworker.com/wp-content/uploads/2014/05/

System Bus

Last Updated: October 31, 2005 11:13:27 AM

http://cottageworker.com/wp-content/uploads/2014/05/

The bus is about as simple as can be. It is made of Vero board which is comprised of parallel strips of copper on a .1 inch grid. The card edge holders are optional. See the additional bus pictures for other views of the bus and connectors.

Description

Not much to say here, look at the Bus Definition Rev. B and additional bus pictures for design details.

Issues/todo log

Date Description Status
Dec-2005 Remove +12V and -12V add N1 and N2 Done Rev B
Mar-7-2005 Add input and output signals to bus so logic is not recreated card requiring IO.

Schematics, board layout, and operational description

Revision Production Date Schematic Layout Operational Description
A Last Documented Nov. 1982 Bus Definition Rev. A
B Updated Dec. 2005 Bus Definition Rev. B

http://cottageworker.com/wp-content/uploads/2014/05/

 

My very own MicroElf, designed by Mike Riley.

The Plan is to build an interface card for my System-5 machine and use all the cards on the System-5 bus (video, keyboard, etc) and use the MICROELF as a front- panel/CPU. As well as an interface to the 36 pin connector, the MICROELF memory needs to be disabled (perhaps just removed) so System-5 memory is used.

http://cottageworker.com/wp-content/uploads/2014/05/

The little card at the top is a 7805 based voltage regulator.

System-4 Bus

The system bus card is built from VERO board and uses SIP style sockets and Radio Shack card supports. Each system card connects to the bus with a right angle single row header at the bottom of the card. At the back of the picture is the original power supply everything, is mounted on a piece of plywood. The AC power connector with a built-in switch was added last year.

http://cottageworker.com/wp-content/uploads/2014/05/

System-4 6845 Alpha Numeric Card

The video card is based on a 6845 circuit from the May 1979 issue of Byte magazine. The circuit uses a 6116 2Kx8 Ram and provides dual port access to the RAM for both the system bus (circuit on the right) and video generation (circuit on the left). The circuit does not wait for horizontal or vertical blanking to access the RAM so the picture has a fair amount of “snow” while the video RAM is being updated. The monitor connects via a DB-9 hanging off the side of the card.

http://cottageworker.com/wp-content/uploads/2014/05/