SC708 is a Z80 Single Board Computer (SBC) module designed for the RCBus. It is CP/M, just add a backplane and a Compact Flash module.
- SC708 – Assembly guide
- SC708 – Compatibility
- SC708 – Firmware (SCM S2)
- SC708 – Parts list
- SC708 – Printed circuit board
- SC708 – User guide
- SC700 series information
- SC700 series support
Downloads
- SC708, v1.0, Kit contents sheet (PDF)
- SC708, v1.0, Schematic (PDF)
- SC708, v1.0, PCB design files (OSHWLab)
- SC708, v1.0, Gerber files (ZIP)
Errata
Nothing known
Suppliers
| Kits | Website | From | Currency |
| Small Computers Direct | SCDirect | UK | GBP |
| Stephen C Cousins | Tindie | UK | USD |
| Small Computer Central | Lectronz | UK | Euro/USD |
| PCBs | Website | From | Currency |
| Small Computers Direct | SCDirect | UK | GBP |
| Stephen C Cousins | Tindie | UK | USD |
| Small Computer Central | Lectronz | UK | Euro/USD |
| Assembled and Tested | Website | From | Currency |
| Not available | |||
| Components | |||
| See parts list |
Tindie does not collect VAT for EU countries
Lectronz does collect EU VAT for orders up to 150 EUR
Parts List
| Reference | Qty | Component |
| PCB | 1 | SC708, v1.0, PCB |
| C1 to C6 | 6 | Capacitor, ceramic, 100 nF |
| LED1 | 1 | LED, green, 3mm |
| P1 | 1 | Header, male, 2 row x 40 pin, angled |
| P2 | 1 | Header, female, 1 row x 6 pin, angled |
| P3 | 1 | Header, male, 1 row x 6 pin, angled |
| R1 | 1 | Resistor, 1k, 0.25W |
| R2 to R7 | 6 | Resistor, 10k, 0.25W |
| SW1 | 1 | Switch, tactile button, angled |
| Screw (for spacer) | 1 | Machine screw, 6mm, M3 |
| Spacer | 1 | Spacer, 10mm, M3, nylon |
| U1 | 1 | Z80 CPU, Z84C0008PEG, or Z80 CPU, Z84C0010PEG |
| U2 | 1 | RAM 128k bytes AS6C1008 |
| U3 | 1 | FLASH 128k bytes SST39SF010A |
| U4 | 1 | 74HCT4075 |
| U5 | 1 | 74HCT259 |
| X1 | 1 | Oscillator 7.3728 MHz |
| IC socket 40-pin U1 | 1 | Socket, DIP, 40-pin |
| IC socket 32-pin U2 and U3 | 2 | Socket, DIP, 32-pin |
| IC socket 14-pin U4 | 1 | Socket, DIP, 14-pin |
| IC socket 16-pin U5 | 1 | Socket, DIP, 16-pin |
Printed Circuit Board
User Guide
SC708 is a Single Board Computer (SBC) meaning it can work without any other backplanes or modules. It is based on a Z80 CPU running at 7.3728 MHz, with 128k bytes of RAM, 128k bytes of FLASH ROM (only 32k bytes is usable), and a simple bit-bang serial port. As a single board computer it is powered from the serial port.
The kit includes the Small Computer Monitor pre-programmed into the FLASH ROM. This includes a capable debug/monitor, BASIC, and a CP/M loader.
As there is no power-on reset circuit on this module, it is necessary to press the reset button to begin executing the firmware.
The board is CP/M ready, meaning it has a suitable processor and memory to run CP/M. Just add a backplane and a Compact Flash module to run CP/M. Ideally, a serial port module should also be added.
Input/output port functions
| I/O Address | Read | Write |
| 0x08 (0x08 to 0x0B) | n/a | Status LED (LED 1) Low = ON, high = OFF |
| 0x20 (0x20 to 0x23) | n/a | Serial RTS |
| 0x28 (0x28 to 0x2B) | Serial TXD | Serial TXD |
| 0x30 (0x30 to 0x33) | n/a | RAM bank select RA16 |
| 0x38 (0x38 to 0x3B) | n/a | Memory paging (lower 32k) Low = ROM, high = RAM |
Jumper options
| Jumper | Function |
| none |
Assembly Guide
Below is the suggested order of assembly. A general guide to assembling circuit boards can be found here.
- Header socket P2
This should lay flat against the PCB - Resistors R1 to R7
These can be fitted either way around - Decoupling capacitors C1 to C6
These can be fitted either way around - Sockets for U1 to U5
Fit such that the notch in the socket matches the curve in the outline on the PCB silkscreen - Bus header P1
Make sure the pins are parallel to the PCB so that the board is vertical when it is fitted into a backplane socket - Header pins P3
Ensure the pins are parallel to socket P2 - Light emitting diode LED1
Fit such that the short lead and/or small flat on the plastic is at the end marked with a line on the PCB silkscreen - Reset switch SW1
- Oscillator X1
Ensure the orientation matches the PCB silkscreen, noting the sharp corner at pins 1 - Insert the integrated circuits into their sockets
Make sure the notch in the component is at the end indicated by the notch in the socket and the curve on the PCB silkscreen - Fit the nylon spacer in the mounting hole
Compatibility
This module conforms to the RCBus specification v1.0 for RCBus-2014 and RCBus-Z80.
The RCBus specification includes RCBus-2014 (both RC2014 standard 40-pin bus and RC2014 enhanced 60-pin bus) and also the full 80-pin RCBus. The 80-pin RCBus provides support for advanced Z80 features, such as the interrupt daisy-chain, as well as support for other processor families.
The table below indicates electrical compatibility with each backplane type (40, 60 and 80 pin)
| Backplane | ? | Compatibility notes |
| RCBus 80-pin |  | Fully supported |
| RCBus 60-pin (RC2014 enhanced) | | Fully supported |
| RCBus 40-pin (RC2014 standard) | | Limitations: Some optional signals are not available (/NMI, /WAIT, /RFSH, /HALT, /BUSAK, /BUSRQ) |
The following table indicates electrical compatibility with SC708. Check firmware and software details for any required software support.
| Product (80-pin) | ? | Compatibility notes |
| SC126 Z180 motherboard |  | Function conflict |
| SC701 Backplane 6+1 | | Adds 6 module sockets RCBus 80-pin and PSU |
| SC702 Backplane 6+1 | | Adds 6 module sockets RCBus 80-pin |
| SC703 Power from 12v | | Adds power supply (8 to 12 volt input) and reset |
| SC704 I2C bus master | | Adds I2C bus master |
| SC705 Serial ACIA | | Adds one serial port Typically set to 0x40 |
| SC706 Z80 CPU | | Function conflict |
| SC707 Memory 128k | | Function conflict |
| SC708 Z80 SBC | | Adds CPU, ROM, RAM Function conflict |
| SC709 Backplane 12+1 | | Adds 12 module sockets RCBus 80-pin and PSU |
| SC710 Backplane 12+1 | | Adds 12 module sockets RCBus 80-pin |
| SC711 Prototyping | | Prototyping module |
| SC712 Power from 5v | | Adds power supply (5 volt input) and reset |
| SC713 RCBus tool | n/a | Simple reference tool No electrical function |
| SC714 Memory 512k | | Function conflict |
| SC715 Compact flash | | Adds Compact Flash storage |
| SC716 Z80 SIO/2 | | Adds two serial ports Typically set to 0x84 |
| SC717 Z80 PIO | | Adds parallel I/O using Z80 PIO |
| SC718 Z80 CTC | | Adds counter/timer using Z80 CTC |
| SC719 Digital I/O | | Adds digital I/O Eight in, eight out |
| SC720 Z80 motherboard | | Function conflict |
| SC721 Memory 512k | | Function conflict |
| SC722 Z180 CPU | | Function conflict |
| SC723 Backplane 3 | | Adds 3 module sockets RCBus 80-pin |
| SC724 Breakout | | Prototyping breakout module |
| SC725 SIO+CTC | | Adds two serial ports and 4 counter/timers |
| SC726 Clock generator | | Generates CLK and CLK2 bus signals |
| SC727 Real time clock | | Adds real time clock for time and date |
| SC728 Module riser | | Simple module riser for RCBus 80-pin |
| SC791 Z80 system | | Function conflict |
| SC792 Z180 system | | Function conflict |
| Product (40 pin) | ? | Compatibility notes |
| SC114 Z80 motherboard | | Function conflict |
| SC130 Z180 motherboard | | Function conflict |
| SC133 Backplane 11+1 | | Adds 11 module sockets RCBus 40-pin and PSU |
| SC134 LED output port | | Adds eight LED outputs |
| SC135 Digital output port | | Adds eight digital outputs |
| SC136 Digital input port | | Adds eight digital inputs |
| SC137 I2C bus master | | Adds I2C bus master |
| SC139 Serial ACIA | | Adds one serial port Typically set to 0x40 |
| SC141 Backplane 12+1 | | Adds 12 module sockets RCBus 40-pin |
| SC142 Power from 12v | | Adds power supply (8 to 12 volt input) and reset |
| SC143 Flash ROM | | Function conflict |
| SC145 Compact flash | | Adds Compact Flash storage |
| SC147 Backplane 6+1 | | Adds 6 module sockets RCBus 40-pin |
| SC148 Power from 5v | | Adds power supply (5 volt input) and reset |
| SC149 Z80 CPU | | Function conflict |
| SC150 Paged RAM 128k | | Function conflict |
| SC151 Paged ROM 128k | | Function conflict |
| Other suppliers | ? | Compatibility notes |
| RC2014 Mini system | | Function conflict |
| RC2014 Pro system | | Function conflict |
| RC2014 Zed system | | Function conflict |
| RC2014 Micro module | | Function conflict |
| RC2014 Backplane 5 | | Adds 5 module sockets RC2014 40-pin |
| RC2014 Backplane 8 | | Adds 12 module sockets RC2014 40-pin |
| RC2014 Backplane Pro | | Adds 12 module sockets RC2014 40-pin / 60-pin |
| RC2014 Z80 CPU | | Function conflict |
| RC2014 SIO/2 dual serial | | Adds two serial ports at 0x80 to 0x87 |
| RC2014 Compact flash | | Adds Compact Flash at 0x10 to 0x17 |
| RC2014 Dual clock | | Generates CLK and CLK2 bus signals |
| RC2014 Pageable ROM | | Function conflict |
| RC2014 64k RAM | | Function conflict |
| RC2014 Memory 512k | | Function conflict |
| RC2014 Digital I/O | | Adds eight LED outputs and eight push buttons |
| RC2014 Real time clock | | Adds real time clock for time and date |
| RC2014 RP2040 VGA terminal | | Connect VGA monitor and USB keyboard |
| RC2014 Pi Pico terminal | | Connect VGA monitor and USB keyboard |
| RC2014 YM2149 sound card | | Adds authentic retro sound |
| Weird electronics Flock v2 | | Adds floppy disk and real time clock |
Notes
- This product is designed for hobby use and is not suitable for industrial, commercial, or safety-critical applications.
- The product contains small parts and is not suitable for young children.
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