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 does not make use of the Z180’s on-board peripherals, such as the serial ports.

Native Z180 Mode

There are two recommended firmware options: Small Computer Monitor (SCM) and RomWBW. With memory module SC119 you can install both options 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 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 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 0x40 to 0x7F.

Download SCM configuration S5

Native Z180 Mode, RomWBW

This configuration (RCZ180_nat) of RomWBW features:

  • <TODO>

Download RomWBW configuration RCZ180_nat


Z80 Replacement Mode

The recommended firmware is the Small Computer Monitor (SCM) configuration S4, available here. This configuration features:

  • In many cases the module is a drop in replacement for a simple Z80 module. However, it may require a 7.3728 MHz oscillator to maintain compatibility with existing software and hardware.
  • This configuration of SCM is for a 32k byte ROM from 0x0000 to 0x7FFF, with 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!
  • 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.

Download SCM configuration S4

Homebrew 8-bit retro computing