SC730 is a Z80 CPU, clock and memory management unit (MMU) module designed for the RCBus. This module’s memory management unit enables 1MB linear memory modules to be used, such as SC721, suitable for running RomWBW.
- SC730 – Assembly guide
- SC730 – Compatibility
- SC730 – Firmware: RomWBW RCZ80_std
- SC730 – Firmware: SCM S7
- SC730 – Parts list
- SC730 – Printed circuit board
- SC730 – User guide
- SC700 series information
- SC700 series support
Downloads
- SC730, v1.0, Kit contents sheet (PDF)
- SC730, v1.0, Schematic (PDF)
- SC730, v1.0, PCB design files (OSHWLab)
- SC730, 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 | SC730, v1.0, PCB |
| C1 to C6 | 6 | Capacitor, ceramic, 100 nF |
| JP1 | 1 | Header, male, 2 row x 2 pin, straight |
| Jumper | 1 | Jumper shunt |
| P1 | 2 | Header, male, 2 row x 40 pin, angled |
| R1 to R5 | 5 | Resistor, 10k, 0.25W |
| 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 | 74AHCT139 |
| U3 | 1 | 74HCT688 |
| U4 | 1 | 74HCT273 |
| U5 | 1 | 74HCT157 |
| X1 | 1 | Oscillator 7.3728 MHz |
| IC socket 40-pin U1 | 1 | Socket, DIP, 40-pin |
| IC socket 20-pin U2 and U5 | 2 | Socket, DIP, 20-pin |
| IC socket 16-pin U3 and U4 | 2 | Socket, DIP, 16-pin |
| IC socket 14-pin X1 | 1 | Socket, DIP, 14-pin Not recommended |
Printed Circuit Board
User Guide
SC730 provides a Z80 central processing unis (CPU), a clock oscillator (typically 7.3728 MHz) and a memory management unit (MMU). The memory management unit provides a 20-bit ddress bus allowing a linear (or flat) 1 MB memory module, such as SC721) to be used.
Typically, the memory module will contain 512k bytes of FLASH ROM and 512k bytes of static RAM, with the ROM mapped to the bottom of the memory map and the RAM to the top.
The 1MB of physical memory is divided into 32 banks of 32k bytes. The MMU maps the top 32k bytes of physical RAM to the top 32k bytes of the Z80 memory maps (0x8000 to 0xFFFF). The lower 32k bytes of the Z80 memory map can be any 32k bank of physical memory. This configuration is suitable for running RomWBW and CP/M.
At reset, the bottom 32k bytes of the 512k byte FLASH ROM are mapped to the bottom 32k bytes of the Z80’s memory space (0x0000 to 0x7FFF).
Any of the sixteen 32k byte FLASH ROM banks (0 to 15) or any of the sixteen 32k byte RAM banks (16 to 31) can be mapped to the bottom 32k bytes of the Z80’s memory space (0x0000 to 0x7FFF) with a single write to I/O address 0x78 (or 0x79). The value written to this I/O address is two times the bank number. Bits 0, 6 and 7 are ignored. This scheme has been used for compatibility with existing software.
Input/output port functions
| I/O Address | Read | Write |
| 0x78 (0x78 to 0x79) | n/a | Memory bank select Bits 1 to 5 = Bank number (x2) Bit 5 = RAM (hi), FLASH (lo) |
Jumper options
| Jumper | Function |
| JP1 | Clock signals JP1.1 connects CPU clock to oscillator X1 JP1.2 connects CPU clock to bus CLK signal |
The default is to connect the output of clock oscillator X1 to the CPU and the RCBus CLK pin. This requires a jumper shunt in each of the two marked default positions (JP1.1 and JP1.2). If you wish to use a clock sourced from a different module then the X1 jumper should be removed.
Assembly Guide
Below is the suggested order of assembly. A general guide to assembling circuit boards can be found here.
- Decoupling capacitors C1 to C6
These can be fitted either way around - Resistors R1 to R5
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
A socket for X1 is not recommended as the oscillator is large, so may touch another module, and heavy, so can fall out if not restrained - 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 JP1
- Fit oscillator X1
Ensure the orientation matches the silkscreen - 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
Fit a jumper shunt in the position shown below.
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) |  | A16 to A19 not supported |
| RCBus 40-pin (RC2014 standard) | | A16 to A19 not supported |
The following table indicates electrical compatibility with SC730. 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 |
| SC702 Backplane 6+1 | | Adds 6 module sockets RCBus 80-pin |
| SC703 Power from 12v | | Adds power supply 8 to 15 volts input |
| SC704 I2C bus master | | Adds I2C bus master and I2C EEPROM |
| SC705 Serial ACIA | | Adds one serial port Typically set to 0x40 |
| SC706 Z80 CPU | | Function conflict |
| SC707 Memory 128k | | Function conflict |
| SC708 Z80 SBC | | Function conflict |
| SC709 Backplane 12+1 | | Adds 12 module sockets RCBus 80-pin |
| SC710 Backplane 12+1 | | Adds 12 module sockets RCBus 80-pin |
| SC711 Prototyping | | Prototyping module |
| SC712 Power from 5v | | Adds power supply 5 volts input |
| 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 | | Adds 512kB ROM and 512kB RAM |
| 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 |
| SC729 Compact flash | | Adds Compact Flash storage |
| SC730 Z80 CPU + MMU | | Function conflict |
| 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 | | 80-pin backplane required |
| 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 | | 80-pin backplane required |
| SC142 Power from 12v | | Adds power supply 8 to 15 volts input |
| SC143 Flash ROM | | Function conflict |
| SC145 Compact flash | | Adds Compact Flash storage |
| SC147 Backplane 6+1 | | 80-pin backplane required |
| SC148 Power from 5v | | Adds power supply 5 volts input |
| 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 | | 80-pin backplane required |
| RC2014 Backplane 8 | | 80-pin backplane required |
| RC2014 Backplane Pro | | 80-pin backplane required |
| RC2014 Z80 CPU | | Function conflict |
| RC2014 SIO/2 dual serial | | Adds two serial ports at address 0x80 to 0x87 |
| RC2014 Compact flash | | Address conflict |
| RC2014 Dual clock | | Generate CLK2 only Conflict on CLK signal |
| 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.
- RomWBW is copyright Wayne Warthen and has been provided free of charge with his permission.
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