SC111 – Firmware

There are two ways to use SC111, Z180 CPU Module:

  • As a replacement for a Z80 module. This gives good software and hardware compatibility, but may not make use of the Z180’s on-board peripherals, such as the serial ports. The recommended firmware is:

Please note that the Z80 replacement (or legacy) mode assumes the Z180 CPU module (SC111) is being used to replace a standard Z80 CPU module in an otherwise ‘standard’ RC2014 set up. This mode is NOT compatible with the Z180 1Mbyte linear memory module (SC119).


Native Z180 Mode

Native mode uses the Z180 CPU’s memory manager which assumes a 1Mbyte linear memory space. It therefore requires a linear memory module, such as SC119.

There are two recommended native mode firmware options:

With memory module SC119 you can install both options together as it has two ROM/Flash sockets.

The Z180 native mode SCM (configuration S5) is available here.

The Z180 native mode RomWBW (configuration RCZ180_nat) is available here.

There are (or were) two inconsistencies between these configurations of SCM and RomWBW which might catch you out:

  • Default baud rates.
    • SCM uses 115200
    • RomWBW v3.x uses 115200
    • RomWBW v2.x uses 38400
  • Mapping of the Z180’s internal I/O registers:
    • SCM uses 0x40 to 0x7F (Note: I might change this)
    • RomWBW uses 0xC0 to 0xFF

Both options require a memory module designed for the Z180 CPU, such as SC119. This has a simple ‘linear’ memory map with 512k bytes of ROM (usually Flash) at the bottom of the physical memory space, and 512k bytes of RAM at the top.

SC119, Z180 memory module

Note, the official RC2014 “512k ROM 512k RAM RomWBW module” is not suitable. This module includes its own memory management, so is not compatible with the simple ‘linear’ memory assumed by these firmware configurations.

In order to support the extra address lines needed for 1M byte of memory, a suitable backplane is required, such as SC112 or SC116.

Native Z180 Mode, SCM

This configuration (S5) of SCM features:

  • Both Z180 serial ports are available with software selection of baud rates.
  • The Z180’s memory management unit (MMU) is used to manage up to 1M byte of memory.
  • The Small Computer Monitor idle events are synchronised to the Z180’s timer.
  • CPU clock source is assumed to be 18.432 MHz. Overclocking, using the Z180’s software controlled clock multiplier, may be possible at 36 MHz.
  • The Z180’s internal I/O addresses are located from 0xC0 to 0xFF.

Download SCM configuration S5

Native Z180 Mode, RomWBW

This configuration (RCZ180_nat) of RomWBW features:

  • A robust ROM based operating system
  • Includes CP/M and Z-System
  • Includes useful utilities and other software
  • Supports a wide range of hardware

Download RomWBW configuration RCZ180_nat


Z80 Replacement Mode

Z80 replacement (or legacy) mode assumes the Z180 CPU module (SC111) is being used to replace a standard Z80 CPU module in an otherwise ‘standard’ RC2014 set up. This mode is NOT compatible with the Z180 1Mbyte linear memory module (SC119).

There are two recommended legacy mode firmware options:

Legacy Z180 Mode, SCM

This configuration (S4) of SCM features:

  • Configures the Z180 CPU module (SC111) as a drop in replacement for a simple Z80 module, in an otherwise ‘standard’ RC2014 set up. However, it may require a 7.3728 MHz oscillator to maintain compatibility with existing software and hardware.
  • It supports a memory map with a 32k byte ROM from 0x0000 to 0x7FFF, and 32k bytes of RAM from 0x8000 to 0xFFFF.
  • Existing CP/M configurations can be used, providing the memory board(s) support paging out ROM, by a write to I/O address 0x38, and allow a full 64k bytes of RAM to be enabled.
  • The official RC2014 “512k ROM 512k RAM RomWBW module” can be used with the Z180 module. Not tested this myself, but it should work.
  • The “#65 Memory Module (512k RAM + 512k ROM)” from Rotten Snow (Karl to his friends) can be used. I’ve not tested this myself, but Karl says it works.
  • The Small Computer Monitor and existing CP/M builds can be used with most common RC2014 compatibile serial modules. However, this configuration does not support the Z180’s on-board serial ports.
  • The Z180’s internal I/O addresses are located from 0xC0 to 0xFF.

Please note that SCM S4 is NOT compatible with the Z180 1Mbyte linear memory module (SC119) and does not support the Z180 CPU’s serial ports.

If the serial module, or any other module, requires an RC2014 standard 7.3728 Mhz bus clock then the 18.432 MHz oscillator typically used for the Z180 CPU will need to be replaced with a 7.3728 MHz oscillator.

Download SCM configuration S4

Homebrew 8-bit retro computing