This page outlines the options available in the RC2014 bus compatible, SC100 series of modules and backplanes.

The SC100 series includes products designed for both the standard RC2014 bus (40-pin) and the enhanced RC2014 bus (> 40-pin). All of the modules (except backplanes) that only use the 40-pin bus connector are in the low profile (25mm) format, while the enhanced bus modules are in the standard (50mm) format.

Standard bus (40-pin) modules work with enhanced bus (> 40-pin) backplanes and can be used along side enhanced bus modules. Most enhanced bus modules work with standard bus backplanes, although some will be function limited.

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

SC100 series PCBs are offered in a range of colours as individual boards and as parts of kits. In addition, the design files are available for you to have your own boards manufactured in other colours.

This table shows products using the standard bus (40-pin).

Standard 40-pin bus
Backplanes	Blue	Green	Black	White	Red
SC133 – 11+1 slot, power
SC141– 12+1 slot
SC147 – 6+1 slot
Motherboards	Blue	Green	Black	White	Red
SC114 – Z80 board
SC130 – Z180 board
Power supply modules	Blue	Green	Black	White	Red
SC142 – 12-volt input
SC148 – 5-volt input
Processor modules	Blue	Green	Black	White	Red
SC149 – Z80 CPU
Memory modules	Blue	Green	Black	White	Red
SC143 – Flash ROM
SC150 – Paged RAM
SC151 – Paged ROM
Storage modules	Blue	Green	Black	White	Red
SC145 – CompactFlash
Serial port modules	Blue	Green	Black	White	Red
SC139 – 68B50 ACIA
Digital I/O modules	Blue	Green	Black	White	Red
SC134 – 8 LEDs
SC135 – 8 outputs
SC136 – 8 inputs
Prototyping modules	Blue	Green	Black	White	Red
see enhanced bus
Other modules	Blue	Green	Black	White	Red
SC137 – I2C bus master

This table shows products using the enhanced bus (> 40-pin).

Enhanced >40-pin bus
Backplanes	Blue	Green	Black	White	Red
SC112 – 6+1 slot, power
SC113 – 6+1 slot
SC116 – 3-slot
Motherboards	Blue	Green	Black	White	Red
TODO? – Z80 board
SC126 – Z180 board
Power supply modules	Blue	Green	Black	White	Red
see standard bus
Processor modules	Blue	Green	Black	White	Red
SC108 – Z80 processor
SC153 – Z80 CPU
SC111 – Z180 CPU
Memory modules	Blue	Green	Black	White	Red
SC152 – Z80 memory
SC119 – Z180 memory
Storage modules	Blue	Green	Black	White	Red
see standard bus
Serial port modules	Blue	Green	Black	White	Red
SC104 – Z80 SIO/2
SC110 – Z80 SIO/2 + CTC
SC132 – Z80 SIO/0
Digital I/O modules	Blue	Green	Black	White	Red
SC129 – 8 in, 8 out
SC103 – Z80 PIO
Prototyping modules	Blue	Green	Black	White	Red
SC115 – Breakout
Other modules	Blue	Green	Black	White	Red
SC102 – Z80 CTC timer

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!

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?

Do you need the enhanced bus?

Most systems do not need the enhanced bus. The enhanced bus includes some extra signals but these are only needed for a minority of applications. To provide the extra signals, at least some of the second row of bus pins are required.

The standard bus has the advantage of simplicity and less soldering. Also, the modules are easier to insert and remove. Notice how, using standard header pins, the Standard bus module (below, right) overhangs more than the Enhanced bus module (below, left) making it to easier to pull out of a bus socket.

What bits do you need?

An RC2014 bus compatible system is made up of either a motherboard and optional extra modules, or a backplane and a number of modules.

A typical minimal system requires:

• Backplane (to connect the modules)
• Power supply
• Reset circuit
• A clock
• 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 by plugin modules.

Motherboards

Motherboards are essentially a single board computer (SBC) with bus sockets for expansion. All SC100 series motherboards have a horizontal bus connectors to allow modular backplane sections to be added.

Motherboards
Standard bus	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	No	Yes 5 volts
Power in via module	Optional	Optional
RAM (kB)	128	512
ROM (kB)	32	512
Firmware	SCM	RomWBW
Serial ports	1	2
Baud rate	9600	300 to 115200
Status LEDs	1	1
Storage	None	SD card
Storage via module	Optional CF card	Optional CF card
Other	None	None
Vertical bus sockets	3	1
Horizontal bus socket	Yes	Yes
Enhanced bus	SC126
CPU	Z180
Clock (MHz)	18.432
Reset	Yes
Supervisor	Yes
Power in via serial	Yes 5 volts
Power in connector	Yes 5 volts
Power in via module	Optional
RAM (kB)	512
ROM (kB)	2 x 512
Firmware	SCM RomWBW
Serial ports	2
Baud rate	300 to 115200
Status LEDs	8
Storage	SD card
Storage via module	Optional CF card
Other	I2C SPI RTC
Vertical bus sockets	2
Horizontal bus socket	Yes

Backplanes

Most SC100 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.

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

Backplanes come in a range of different lengths, enabling small and large systems to be built.

Backplanes
Standard Bus	SC133	SC141	SC147
Bus pins	40	40	40
Vertical sockets	11	12	6
Horiontal socket	Yes	Yes	Yes
Horzontal 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
Enhanced Bus	SC112	SC113	SC116
Bus pins	80	80	80
Vertical sockets	6	6	3
Horizontal socket	Yes	Yes	No
Horizontal plug	No	Yes	No
Power input	5 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

Power supply

There are several ways to power an SC100 series system:

• From a USB to serial adapter. SC100 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.

• Another option is to power an SC100 series system from a power module. Power modules also provide a good quality clean reset signal and status indicator lights.

The first method of powering the system typically takes the power from a modern computer via a USB socket. The other two methods generally require a wall-mounted (wall-wart) power adapter.

Power modules
Standard bus	SC142	SC148
Form factor	Low profile	Low profile
Voltage input	8-12 volt	5 volt
Max current	1 amp	1 amp
Reset	Yes	Yes
Supervisor	Yes	Yes
Status LEDs	2	2
Enhanced bus compatible	Yes	Yes
Enhanced bus	n/a
Form factor
Voltage input
Max current
Reset
Supervisor
Status LEDs
Standard bus compatible

Processor

The SC100 series offers a choice of two microprocessors:

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

• The Z180 was introduced later as advances in integrated circuit manufacture allowed more complex designs.

The Z180 is essentially software compatible with the Z80 but includes extra functions such as serial ports. The Z180 allows physically smaller systems to be created and also reduces the system cost.

Currently, to run RomWBW on an SC100 series system you require a Z180 processor.

If you want a system nearest to an authentic 1980 computer you should use the Z80 processor. If you are willing to use later technology then a Z180 based system will be a good choice.

Processor modules
Standard bus	SC149
CPU	Z80
Clock (MHz)	7.3728
Reset	No
Supervisor	No
RAM (kB)	None
ROM (kB)	None
Serial ports	None
Baud rate	n/a
Firmware	SCM
Enhanced bus compatible	Yes
Enhanced bus	SC108	SC111	SC153
CPU	Z80	Z180	Z80
Clock (MHz)	7.3728	18.432	7.3728
Reset	Yes	Yes	Yes
Supervisor	Yes	Yes	Yes
RAM (kB)	128	No	128
ROM (kB)	32	No	127
Serial ports	None	2 x 115k	None
Baud rate	n/a	300 to 115200	n/a
Firmware	SCM	None	SCM
Standard bus compatible	Some limitations	No	Some limitations

Memory

Typical Z80 systems in 1980 had 64k bytes of RAM. It is possible to have more than 64k bytes of RAM on a Z80 system but it is easier to implement significantly larger memory maps with the Z180 processor.

Memory modules
Standard bus	SC143	SC150	SC151
RAM (kB)	None	128	None
ROM (kB)	4 x 128 FLASH	None	4 x 128 FLASH
Firmware	SCM	None	SCM
For CPU	Z80	Z80	Z80
Status LEDs	None	1	1
Bus pins	40	40	40
Enhanced bus compatible	Yes	Yes	Yes
Enhanced bus	SC119	SC152
RAM (kB)	512	128
ROM (kB)	2 x 512	4 x 32
Fimrware	SCM RomWBW	SCM
For CPU	Z180	Z80
Status LEDs	None	2
Bus pins	80	50+
Standard bus compatible	No	Yes

Serial ports

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.

Some processor modules and all motherboards include one or more serial ports:

• SC111 has two serial ports. These have software-selectable baud rates. These ports are included in the Z180 CPU.

• SC114 has one serial port. This is a very basic “bit-bang” port running at 9600 baud.

SC126 and SC130 both have two high-speed serial ports.

Serial ports can also be provided by dedicated cards:

• SC110 has two serial ports (Z80 SIO) and a four-channel counter/timer (Z80 CTC). The second serial port has software-selectable baud rates controlled by one of the counter/timer channels.

• SC132 has two serial ports typically fixed at 115200 baud.

• SC139 has one serial port (68B50 ACIA) fixed at 115200 baud.

Serial modules
Standard bus	SC139
Ports	1
Baud rate	115200
Baud rate control	None
Device	68B50 ACIA
Extras	None
Enhanced bus compatible	Yes
Enhanced bus	SC104	SC110	SC132
Ports	2	2	2
Baud rate	115200	300 to 230400	115200
Baud rate control	Osc Bus clk	Port B via CTC	Osc Bus clk
Device	SIO/2	SIO/2	SIO/0
Extras	None	Timers	None
Standard bus compatible	Some limitations	Some limitations	Some limitations

Storage

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. Two solutions are currently offered:

• CompactFlash cards provide fast file access. SC145 allows CompactFlash cards to be used for CP/M and RomWBW.

• SD cards. The Z180 motherboards, SC126 and SC130, provide a port for connecting a MicroSD card adapter. This is supported by RomWBW.

Storage modules
Standard bus	SC145
Device	Compact Flash
Enhanced bus compatible	Yes
Enhanced bus	SC154
Device	Compact Flash
Standard bus compatible	Yes

Digital I/O modules

Digital input/output modules can include signals to interface to external electronics and/or LEDs and switches. Input/output signals can either be fixed input or outputs, or they can be programmable bi-directional signals.

Digital I/O modules
Standard bus	SC134	SC135	SC136
Device	74 series logic	74 series logic	74 series logic
Bi-directional signals	None	None	None
Signal outputs	None	8	None
Output LEDs	Yes (8)	None	None
Signal inputs	None	None	8
Input LEDs	None	None	None
Enhanced bus compatible	Yes	Yes	Yes
Enhanced bus	SC103	SC129
Device	Z80 PIO	74 series logic
Bi-directional signals	16	None
Signal outputs	None	8
Output LEDs	None	Yes
Signal inputs	None	8
Input LEDs	None	Yes
Standard bus compatible	Yes	Yes

Prototyping modules

Prototyping modules
Standard bus	n/a
Features
Enhanced bus compatible
Enhanced bus	SC115
Features	Breakout Decoding
Standard bus compatible	Some limitations

Other modules

Other modules
Standard bus	SC137
Features	I2C bus
Enhanced bus compatible	Yes
Enhanced bus	SC102
Device	Z80 CTC (4 timers)
Standard bus compatible	Some limitations

Example systems

• System #1: Minimal Z80 computer. Includes the Small Computer Monitor, BASIC, but no storage.
  • SC114 – Z80 motherboard with memory and 9600 baud serial port

• System #2: Z80 computer with CP/M and CompactFlash file storage
  • SC114 – Z80 motherboard with memory and 9600 baud serial port
  • SC145 – CompactFlash interface module for file storage
  • A dedicated serial module is recommended but not essential:
    • SC139 – Single serial port (68B50 ACIA)
    • SC132 – Two serial ports (Z80 SIO)
    • SC110 – Two serial ports (Z80 SIO) plus timer (Z80 CTC)

• System #3: Z80 computer with CP/M and CompactFlash file storage
  • SC112 – Backplane
  • SC108 – Z80 processor module (CPU, RAM, ROM)
  • SC145 – CompactFlash interface module for file storage
  • SC139 – Single serial port (68B50 ACIA)
    • Or perhaps a two-channel serial module:
      • SC132 – Two serial ports (Z80 SIO)
      • SC110 – Two serial ports (Z80 SIO) plus timer (Z80 CTC)

• System #4: Z180 computer with RomWBW CP/M and SD card file storage
  • SC130 – Z180 motherboard

• System #5: Z180 advanced computer with SD card for storage. Includes SCM and RomWBW CP/M.
  • SC126 – Z180 motherboard

• System #6: Z180 computer with CP/M and CompactFlash file storage. Includes SCM and RomWBW CP/M.
  • SC112 – Backplane
  • SC111 – Z180 CPU module with 2 serial ports
  • SC119 – Z180 memory module
  • SC145 – CompactFlash interface module for file storage