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SBC V2 (web pages currently being reformatted b1ackmai1er 1/12/2020)

The SBC V2 is a Zilog Z80 processor board. It's a 100x160mm board that is capable of functioning both as a standalone SBC or as attached to the ECB bus.

Previously known as the N8VEM SBC, development began in 2006 wth V1 and is currently still in development.

For most people, the SBC-V2-004 offers the most convenience and functionality.


  • 4Mhz+ Zilog Z80 CPU.
  • Up to 512Kb paged SRAM.
  • Up to 1Mb EPROM or 512Kb Flash ROM.
  • Serial Interface.
  • IDE interface.
  • Real Time Clock.
  • Onboard sound.
  • Battery backup for RTC and SRAM via super capacitor.
  • Standard ECB bus interface.
  • +5V power connector for Single Board Computer operation.
  • Reset button.
  • Status LED.

Software Support

ROMWBW BIOS featuring:

  • CP/M / ZSDOS
  • RAM & ROM disk support.
  • ROM based BASIC, FORTH and Monitor.
  • Prebuild disk images

ROMWBW Eurocard expansion board driver support:

  • VDU
  • CVDU
  • VGA3
  • Zilog Peripherals
  • Disk I/O
  • 4PIO
  • SCG
  • DSKY
  • MF-PIC

Version History

VersionDetailsKey feature
SBC V1Initial versionRuns as Single Board Computer or on Euro Card Bus.
SBC V2-003Enhanced versionBattery backed RAM support, Serial jumper options, RAM and ROM configuration options.
SBC V2-004Extended versionIDE connector, sound, Clock speed control, Super capacitor for RAM and RTC backup.
SBC V2-005In development1Mb Flash support.


The DS1302 real time clock can be set under CP/M using the rtc utility program.

Loading CPM...
CP/M-80 Version 2.2C for the N8VEM, October 2008
Run XM from A drive, this downloads file to B drive
Start RTC Program
RTC: Version 1.0
RTC: Commands: E)xit T)ime st(A)rt S)et R)aw L)oop C)harge N)ocharge D)elay I)nit G)et P)ut H)elp
RTC: trickle charger disabled.

Set the time and date with the Init command first and then use the Set command to program it.

RTC.COM can also be used to set up trickle charging for the backup battery or super capacitor if connected. More Information on charging Super Capacitors can be found here:

The utility can also set and read the RTC memory.

RTC.COM is part of Wayne Warthen's ROMWBW package.

One Bit Input Port

Bit 6 of RTC port $70 is connect to an on board jumper JP2 which can be read by software. By default it is tied high. Removing jumper JP2 will result in the being tied low (=0).

Effectively this creates a configurable jumper setting which the ROMWBW bootrom can use for determining the primary communications console.

This facility is not enabled by default in ROMWBW and the setting is ignored. To enable, rebuild the ROMWBW package with the CRTACT setting set to true. The CRT type can also be configured at this time:



This will cause ROMWBW to check the status of BIT 6 at startup. If “0” (jumper removed) it will change the primary communications console from the Serial UART to the first CRT console found. If a CRT console is not found it will default back to the Serial UART. If BIT 6 = “1” (jumper in place) it will boot as normal with the primary console using the Serial UART.

boards/sbc/sbc_v2/start.1606819145.txt.gz · Last modified: 2020/12/01 05:39 by b1ackmai1er
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