SC119, v1.0, Description

SC119 is a memory module designed to work with the Z180 CPU.

SC119 Memory Module

The module contains two 512k byte Flash ROM chips and one 512k byte RAM chip. Only one of the Flash ROM chips can be mapped into memory at any given time.

A jumper, or external switch, selects which of the Flash ROM chips is used. Alternatively, an external control signal could be connected to the switch header and used to control selection. By this method it would be possible to access all 1024k bytes of Flash memory.

The memory is organised in a 1M byte linear memory space. In order for a Z80 family CPU to access 1M byte of memory, some form of memory management (eg. paging) is required. As this module does not include such a feature, memory management must be provided elsewhere. The Z180 CPU includes a suitable memory management, but the standard Z80 CPU does not.

While it is possible to build a Z80 module with on-board memory management hardware, it is assumed this memory module will be used with a Z180 CPU, such as SC111.

SC111 Z180 CPU module

The Flash memory supports being written to by the CPU, thus allowing the firmware to be updated, or “Flashed”. This is unlikely to happen by accident due to the software requirements for writing to the Flash, but to play safe each Flash chip has a jumper to select hardware write protection.

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