This page outlines the options available in the SC600 series of modules and backplanes for the 40-pin RCBus. This range uses the 40-pin RCBus for simplicity and compatibility with RC2014.

The SC600 series includes products designed to meet the requirements of the RCBus v1.0 specification for 40-pin systems.

The designs are open source with full details of the schematics, printed circuit board Gerber files, and software, either on this website or linked from this site. Kits are available for those who would like the convenience and reassurance that kits offer.

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A good place to start is the base system:

• SC691 – Z80 RomWBW, CP/M and SCM system

This is a functional computer that can be purchased, as a kit, in its default configuration and used without further study of the growing range of compatible products.

If you are feeling confident then you can configure your system from scratch with the modules and backplanes listed below. You can even mix and match modules and backplanes designed for the 40-pin RCBus, the 60-pin RCBus, the 80-pin RCBus, and RC2014 and third party “designed for RC2014” products. You will need to examine these products carefully to make sensible choices.

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The following designs are available in the SC600 series.

• SC601 – Z80 CPU module with clock, reset and status LEDs
• SC602 – Memory module, 512KB RAM, 2 x 512KB Flash ROM
• SC603 – Serial module, Z80 SIO/2
• SC604 – Compact Flash module
• SC605 – Digital I/O module, 8 in and 8 out
• SC606 – Real time clock module
• SC607 – Prototyping module
• SC608 – I2C bus master module
• SC609 – Dual servo controller module
• SC610 – Serial module, 68B50 ACIA
• SC611 – Micro SD card module
• SC612 – Serial module, 68B50 ACIA
• SC613 – Compact Flash module
• SC671 – Backplane 6+1, with 5 volt power input
• SC672 – Backplane 6+1, with extension plug
• SC673 – Backplane 10+1, with 5 volt power input
• SC691 – Z80 RomWBW, CP/M and SCM system

In addition, there are compatible backplanes, modules and motherboards in the SC100 series. For example:

• SC133 – Backplane 11+1, with 12 volt power input
• SC141 – Backplane 12+1, with extension plug
• SC147 – Backplane 6+1, with extension plug
• SC142 – Power supply module, 12 volt input
• SC114 – Z80 motherboard with SCM, CP/M ready
• SC130 – Z180 motherboard with RomWBW CP/M

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Obviously, the most important question is: “What colour should it be?”

Printed circuit boards (PCBs) are offered in a range of colours (B=Blue, G=Green, K=Black, W=White, R=Red) as individual boards and, in some cases, as parts of kits. In addition, the design files are available for you to have your own boards manufactured in these or other colours.

Below is a list of products designed for the 40-pin RCBus.

RCBus 40-pin products
Backplanes	Kit		R	B	G	K	W
SC671 – 6+1 slot, 5V in
SC672 – 6+1 slot
SC673 – 10+1 slot, 5V in
See also SC133 – 11+1 slot, 12V in
See also SC141 – 12+1 slot
See also SC147 – 6+1 slot
Motherboards	Kit		R	B	G	K	W
None in SC600 series
See also SC114 – Z80 board
See also SC130 – Z180 board
Power supply modules	Kit		R	B	G	K	W
SC614 – Power
See also SC142 – Power
Processor modules	Kit		R	B	G	K	W
SC601 – Z80 CPU
Memory modules	Kit		R	B	G	K	W
SC602 – Memory, 512k
Storage modules	Kit		R	B	G	K	W
SC604 – Compact Flash
SC611 – Micro SD Card
SC613 – Compact Flash
Serial port modules	Kit		R	B	G	K	W
SC603 – Z80 SIO/2
SC610 – 68B50 ACIA
SC612 – 68B50 ACIA
Digital I/O modules	Kit		R	B	G	K	W
SC605 – 8 in, 8 out
Prototyping modules	Kit		R	B	G	K	W
SC607 – Prototyping
Other modules	Kit		R	B	G	K	W
SC606 – RTC
SC608 – I2C master
SC609 – Servo
Base systems	Kit		R	B	G	K	W
SC691 – Z80 system RomWBW CP/M & SCM

You can make your system with a mix of colours if you really want to stand out from the crowd or if you can’t make your mind up!

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With the difficult colour decision out of the way, the next question is; “What do you want to do with your retro computer?”

Consider the following questions:

• Do you want to just run existing software?
• Do you want to write software?
• Do you want to experiment with hardware?
• Do you want your system in a neat box?
• Will you be making changes to the hardware over time?
• How authentic (retro) do you want your system?
• Do you want to run CP/M?
• Do you want to run RomWBW?

What bits do you need?

A typical minimal system requires:

• Backplane (to connect the modules)
• Power supply
• Reset circuit
• A clock oscillator
• A central processing unit (CPU)
• Memory (RAM and ROM)
• A serial port

These functions can all be provided on a single motherboard or they can be split in a variety of ways on a number of modules. Additional functions can be added with plug-in modules.

Motherboards

Motherboards are essentially a single board computer (SBC) with bus sockets for expansion. There are no motherboards in the SC600 series but you can use SC114 and SC130.

Motherboards	SC114 †	SC130 †
CPU	Z80	Z180
Clock (MHz)	7.3728	18.432
Reset	Yes	Yes
Supervisor	No	Yes
Power in via serial	Yes 5 volts	Yes 5 volts
Power in connector	Yes 5 volts	Yes 5 volts
Power in via module	–	–
RAM (kB)	128	512
ROM (kB)	32	512
Firmware	SCM	RomWBW
Serial ports	1	2
Baud rate	9600	115200
Status LEDs	1	1
Storage	No	SD card
Storage via module	CF card (option)	CF card (option)
Other	None	None
Vertical bus sockets	3	1
Horizontal bus socket	Yes	Yes

† SC114 and SC130 are not part of the SC600 series but they are close to what I would now design for the SC600 series it is not worth changing.

RomWBW includes CP/M and a range of other useful software. It has been produced by Wayne Warthen and included with his permission, free of charge.

SCM is the Small Computer Monitor – a capable monitor for software and hardware development and debugging.

Systems

To make it easier to select the required parts the following are available as complete systems. The details below are for the systems with default options selected when purchasing. In some cases there are options for alternative modules and backplanes to customise the system.

Systems	SC691 †
CPU	Z80
Clock (MHz)	7.3728
Reset	Yes
Supervisor	Yes
Power in via serial	Yes 5 volts
Backplane power in connector	Yes 5 volts 2.1mm
RAM (kB)	512
ROM (kB)	512 x 2
Firmware	RomWBW SCM
Serial ports	2
Serial device	Z80 SIO/2
Baud rate options	2400 to 115200
Baud rate control	Yes (jumpers)
Status LEDs	11
Storage	MicroSD
Other	None
Free vertical bus sockets	10
Horizontal bus socket	Yes
Backplane	SC673
Modules	SC601 SC602 SC603 SC611

† In May 2025 the SC691 kit was upgraded to include a two channel serial module with baud rate options (SC603), replacing the original single channel module (SC610).

Backplanes

Most SC600 series backplanes can be extended by joining backplane sections together. These backplanes have a number of vertical connectors for modules plus a horizontal connector for an additional backplane section or a module.

The horizontal connector can also accept a module, which makes it more accessible for experimenting and debugging hardware.

Backplanes	SC671	SC672	SC673
Bus pins	40	40	40
Vertical bus sockets	6	6	10
Horizontal bus socket	Yes	Yes	Yes
Horizontal bus plug	No	Yes	No
Power input	5 volt 1 amp	No	5 volt 1 amp
Reset	Yes	No	Yes
Supervisor	Option	No	Option
Module spacing	0.6″ 15.24mm	0.6″ 15.24mm	0.6″ 15.24mm

Backplanes	SC133 †	SC141 †	SC147 †
Bus pins	40	40	40
Vertical bus sockets	11	12	6
Horizontal bus socket	Yes	Yes	Yes
Horizontal bus plug	No	Yes	Yes
Power input	8-12 volt 1 amp	No	No
Reset	Yes	No	No
Supervisor	No	No	No
Module spacing	0.6″ 15.24mm	0.6″ 15.24mm	0.6″ 15.24mm

† These are not part for the SC600 series but are fully compatible.

Power supply

There are several ways to power an SC600 series system.

From a USB to serial adapter

SC600 series serial ports have a 5-volt input pin which can be used to power the system. This works for modest size systems but isn’t ideal.

From a backplane

Backplanes can include a power input connector. This is generally preferable to powering from a serial port.

Processor modules

The Z80 was extremely popular in the late 70s and 80s.

Processor	SC601
CPU	Z80
Clock (MHz)	7.3728
Reset button	Yes
Supervisor	Yes
RAM (kB)	None
ROM (kB)	None
Serial ports	None
Baud rate	n/a
Firmware	None
Status LEDs	11
Other	–

Memory modules

Typical Z80 systems in 1980 had 64k bytes of RAM.

Memory	SC602
RAM (kB)	512
ROM (kB)	512 x 2
Fimrware	1: RomWBW 2: SCM
For CPU	Z80
Status LEDs	None

Serial modules

Most systems include at least one serial port. This allows the retro computer to use a terminal, or modern computer acting as a terminal, as the main user interface.

Serial	SC603	SC610	SC612
Ports	2	1	1
Baud rate options	2400 to 115200	115200 only	2400 to 115200
Baud rate control	Yes (jumpers)	No	Yes (jumpers)
Device	Z80 SIO/2	68B50 ACIA	68B50 ACIA
Address options	0x80 or 0x84	Any even address	0x80 or 0x40
Onboard oscillator	Yes 7.3728MHz	Yes 7.3728MHz	Yes 7.3728MHz
Activity LEDs	None	TxD and RxD	None
Control signals	Fixed (Z80)	Z80 or 68xx	Fixed (Z80)
Interrupt options	1	3	1
Interrupt modes	Mode 1 or mode 2	Mode 1	Mode 1
Interrupt daisy-chain	Yes (IEI/IEO)	No	No

Storage modules

If you want to load and save files you will need some form of storage. While it is possible to transfer data to and from a modern computer via a serial port, it is generally better to have some local storage on the retro computer.

Storage	SC604	SC611 †	SC613
Device	Compact- Flash	Micro SD	Compact- Flash
OS support	CP/M RomWBW	RomWBW inc. CP/M	CP/M RomWBW
Speed	Fast	Slow	Fast
Other	Vertical module	Vertical module	Horizontal module

† Support requires RomWBW v3.5 or a customised earlier version.

Digital I/O modules

Digital input/output modules can include signals to interface to external electronics and/or LEDs and switches.

Digital I/O	SC605
Device	74 series logic
Bi-directional signals	None
Signal outputs	Yes (8)
Output LEDs	Yes (8)
Signal inputs	Yes (8)
Input LEDs	Yes (8)

Other modules

Prototyping	SC607
Features	03″ & 0.6″ DIL layout

Real time clock	SC606
Device	DS1302

I2C bus master	SC608
Device	Bit-bang

Servo control	SC609
Device	74 series logic
Channel	2