This page outlines the options available in the RCBus compatible, SC700 series of modules and backplanes.
The SC700 series includes products designed to meet the requirements of the RCBus v1.0 specification.
The RCBus is an extended version of the RC2014 bus. The RCBus has been created for three main reasons:
- To overcome the limitations of the RC2014 bus whilst maintaining compatibility with existing products. This includes support for advanced features, such as the Z80 interrupt priority chain, and support for other processor families.
- To avoid confusion over what is an RC2014 product and what is a third party RC2014 compatible product.
- To reduce the chance of trademark infringement. RC2014 is a trademark belonging to RFC2795 Ltd.
Modules designed for RC2014 can be used with RCBus backplanes, but not all RCBus modules can be used with RC2014 backplanes.
Obviously, the most important question is: “What colour should it be?”
SC700 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.
Below is a list of SC700 series products designed for the RCBus.
|SC701 – 6+1 slot, 5V in|
|SC702 – 6+1 slot|
|SC709 – 12+1 slot, 5V in|
|SC710 – 12+1 slot|
|SC720 – Motherboard|
Power supply modules
|SC703 – Power, 12V in|
|SC712 – Power, 5V in|
|SC706 – Z80 CPU|
|SC708 – Z80 SBC|
|SC707 – Z80 mem, 128k|
|SC714 – Z80 mem, 512k|
|SC715 – Compact Flash|
Serial port modules
|SC705 – 68B50 ACIA|
|SC716 – Z80 SIO/2|
|SIO + CTC ? TODO?|
Digital I/O modules
|SC719 – 8 in, 8 out|
|SC717 – Z80 PIO|
|SC711 – Prototyping|
|SC704 – I2C master|
|SC718 – Z80 CTC|
Most RC2014 compatible modules can be used in an RCBus system.
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?
What bits do you need?
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 are essentially a single board computer (SBC) with bus sockets for expansion. All SC700 series motherboards have a horizontal bus connectors to allow modular backplane sections to be added.
|ROM (kB)||2 x 512k|
Most SC700 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.
There are several ways to power an SC700 series system:
- From a USB to serial adapter. SC700 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 SC700 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.
|Voltage input||8-12 volt||5 volt|
|Max current||1 amp||1 amp|
The SC700 series offers a choice of two microprocessors: (or at least it will do soon!)
- 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.
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.
|Serial ports||None||9600 baud|
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.
|ROM (kB)||2 x 32||512|
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.
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.
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|
|Digital I/O modules||SC717||SC719|
|Device||Z80 PIO||74 series|
|Signal outputs||None||Yes (8)|
|Output LEDs||None||Yes (8)|
|Signal inputs||None||Yes (8)|
|Input LEDs||None||Yes (8)|
|Features||03″ & 0.6″|