A RAM/ROM plug-in to extend the unit to support the CP/M operating system on the TS2068.
An optional module can be plugged into the interface unit to extend the operation of the system to acommodate the CP/M Operating system. The CP/M module consists of a plug in card with 32k bytes of dynamic RAM and a 1K byte ROM installed. Incorporated into the ROM is the ’cold boot’ loader program necessary for system startup in the CP/M mode. The RAM is switched into the system under software (I/O port) control to enable a 64k byte contiguous RAM space Starting from address 0h. This architecture is necessary to support the CP/M operating system. A switch and logic is provided in the interface unit to allow this mode of operation upon power-up. The operating system program is loaded from microdrive tape and runs out of RAM. Thereafter the operating system functions usually performed by disk drives are performed on the microdrive tape.
The requirements of the CP/M operating system dictate inclusion of additional RAM and ROM. To support this the CP/M Module includes 32k bytes of dynamic RAM and a 1k byte ROM. The ROM is enabled upon power-up when in the CP/M mode. The ROM contains code forming the ’cold boot’ loader. Execution of this code enables the system to load additional code from the number 1 microdrive transport into high memory. Control is then passed to the additional code so loaded and this code disables the ROM by writing a bit to an I/O port (see section 4.6 for I/O port map). Upon disabling the ROM in the CP/M mode the software then enables the 32k of additional RAM in the address range 0h to 7FFFh. Whenever the system requires access to the display file memory or the ‘HOME’ ROM, the additional RAM is disabled by the software by means of a bit in an I/O port.
The CP/M Module proper includes only the ‘COLD BOOT ROM’ , the 32k byte dynamic RAM and a data buffer. The control logic for RAM refresh and for enable/disable functions are part of the interface unit electronics. A switch mounted on the front of the case is wired through the module to control entry into CP/M mode upon power-up. The switch is ignored after power-up or if no CP/M module is installed.
The CP/M module is a user installed option. It is supplied as a PCB with a handle and is plugged into the rear of the interface unit after removal of a ‘battery door’ style access cover.
Never released: this description comes from the TS2060 Interface Product Specification document.