The N8 is intended to be a “home brew” style computer in the style of early 1980's all-in-one home computers with a usable set of features such as color graphics, audio, an assortment of mass storage options, a variety of ports, etc. Although a bus expansion is supported no additional boards are required.
The N8 is designed so builders can assemble it themselves using common tools such as basic soldering iron, VOM, etc. It is a simple two-layer board construction using all commonly available plated-through-hole (DIP and PLCC) components without requiring any SMT skills, programmable logic devices, etc.
A quick summary of the N8 features:
|Processor||Z8S180 CPU (Z80 compatible, 33MHz max)|
|Memory||1MB SRAM and 512K Flash boot ROM (in-circuit reprogrammable)|
|Video||TMS9918 Composite Color Video|
|Sound||AY-3-8910 Sound Generator|
|Keyboard/Mouse||PS/2 Keyboard and Mouse|
|Mass Storage||IDE drives (including CF adapter) port, Floppy drives port (3.5“ @ 1.44M/720K, 5.25” @ 1.2M/360K), and SD socket|
|Expansion I/O||Two Serial ports, Parallel Printer port, Two MSX compatible Joystick ports, RTC w/NVRAM (configuration data), RS-485 networking port|
|Other||Various diagnostic LEDs, “front panel” status indicators, buttons, with optional debugging hex display and keyboard (DSKY)|
ROM Support included in
- UNA BIOS
- C-BIOS MSX Compatible BIOS
- Various MSX Game Cartridges supported by C-BIOS
- On release 2312 of the PCB the SD circuit was changed, so the MSX CBIOS needs to be recompiled with different settings to work with older boards
- There have been reports of fragile/missing traces on the 4314 boards (U11-17 to U8-1) and on the 2312 boards (U58-13 to U24-2) both in the SD card circuit
- The version of the MSX CBIOS has been tested on the 4314, 2312 and 2511 versions of the board.
- Board versioning scheme is WWYY where WW is the week number and YY is the year number. So, 2312 means week 23 of year 2012.
Changes and Errata
Successful serial communication with the ZS180 requires the DCD to be low. On the N8 board DCD is pin 47 of the ZS180. This line is tied to ground via resistor R42 (2K2). This resistor value may be too high. If you are unable to see serial output then try bridging this resistor so pin 47 is connected to ground.
|N8-2511 Jumper Settings||Listing of the various Jumper Settings|
|N8-2511 BOM||BOM for release 2511|
|N8-2312 Schematic||Schematic 2312 version|
|N8-2312 Board||Board 2312 version|
|N8-4314 Board and Schematic||ZIP Archive with build files for the 4314 version|
|MSX BIOS||MSX BIOS Software (SD card now works with all versions of board, ROM is compiled for 2312 or newer)|
|N8 Laser Cut Acrylic Case Design||N8 laser cut acrylic case SVG files and assembly pictures|