We816-mark2

WE816-MARK2

The WE816-MARK2 is the second iteration of a 16-bit 65816 based system with 512K of System RAM, 96K of System ROM, a Raspberry PI Pico based graphics processor and an AY-3-8910 Sound chip. The system runs a custom version of BASIC and supports commodore compatible IEC disk drives.

EhBASIC by Lee Davison was ported to the 65816 CPU on the WE816 computer. It is designed to allow a full 64K bank for BASIC code and variables with the BASIC interpreter running in a totally different bank. Full documentation on the basic intrepreter can be found in the support folder

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Bugs:

• V0.08 board U13 should be a 22V10 rather than a 20V8 (no patches required) U31 should be 74ALS245 rather than 74AC245 (no patches required) The Footprints for the expansion(J7) and Keyboard(J3) connectors are wrong -- special cables are required to connect this version to keyboard and expansion RTC IS STILL BROKEN, DO NOT POPULATE U7,U8,X3,C36,C37,C34,R1,R2,R3,U9,BT1,K4,JP1, & JP2

• V0.9 board U16 should not be populated -- the wait state generator is not functional, maximum successful tested clock speed is 2.4576 Mhz Higher CPU speeds are possible, but the video will not function at much beyond this speed.

To Do:

• Document Jumper Settings
• Document IO Ports
• Memory Map
• Video speed is not fast enough to deal with a clock speed > (around) 2mhz (2.4576 works perfectly) Need to add wait state hardware for video
• Add Pictures to this Document

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What is included in this repo?

As of this time, the repo includes

1. The WE816-Mark2 Mainboard PCB Kicad design and Gerber files
2. The source code and binaries for the WE816 BASIC interpreter
3. The source code and binaries for the WE816 BIOS firmware
4. The source code and binaries for several hardware test programs
5. The logic equasions for the 4 GALs
6. **OpenSCAD and STL files for a 3d printed case
7. The Firmware for the Raspberry Pi Pico Video

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Known Bugs

System Jumpers

Jumper P9 -- stereo channel mixer

• no jumpers, channel a left, channel c right, channel b left and right
• 1-2 and 2-3 , channel a,b,c mixed to left and right

Jumper K1 - SRAM chip selection

• 1&2 - 512K chip used (AS6C4008)
• 2&3 - 128K chip used (AS6C1008)

Jumper K2 - ROM chip selection

• 1&2 - 27c256 chip used
• 2&3 - 29c256 chip used

Jumper K3 - ROM size

• 1&2 - 16K rom page 0 memory map @ $C000
• 2&3 - 32K rom page 0 memory map @ $8000

Power P1

• 1- NC
• 2-GND
• 3-GND
• 4-+5VDC 2A Regulated

Reset P2

• NO Switch (Short to put system in reset)

Jumper J1, Interrupt Select

• 1&8 UART Interrupt enabled
• 2&7 VIA 1 Interrupt enabled
• 3&6 VIA 2 Interrupt enabled
• 4&5 TMS9918 Interrupt enabled

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Video Programming

IO PORTS

Bill Of Materials

Mainboard

Keyboard

The Keyboard used in the WE816 is identical to the keyboard used in Sergey Kiselev's MSX compatible OMEGA computer. See the Schematics, PCB layout and build instructions here

Case

The case in the following images is a 3D print manufactured by the 3D print service offered by JLCPCB.com. The case was originally designed to be 3D printed by a FDM printer such as the Anycubic Chiron. It was originally intended that threaded inserts be melted into the stand off posts so the diameter of the holes were sized accordingly. If a printing service (such as JLCPCB) is used that uses resin printing, it is necessary to slightly drill out the holes in the stand offs so that threaded inserts can be glued in. It should also be noted that the design tolerances are quite tight and variations in printing can mean that some slight adjusting may be needed in order to get a good fit.

A 12V to 5V converter can be seen in the image that was added into the case in order to convert the 12V power input to the 5B required by the main board.

Questions?

If there are any questions, I can be reached at vic2020Dan at gmail dot com.

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