Changes
Graduate software provided a version of CP/M+ on ROM. This used two 16KB ROMs which were standard CPC firmware compatible ROMs. You were required to send them your system discs, essentially they provided a transfer service so they didn't infringe on Digital Research's copyright or distribution policy.
Additional 'utility' ROMs (with a custom structure and not CPC firmware compatible) contained CP/M programs installed on a ROM. You could choose which programs you wantedto be installed.
* [[CPM_Accessory_ROM_1]]
== Accessory/Utility ROM ==
A utility ROM can exist in any ROM slot from 1 to 15. They are checked in ascending order. If the identification is correct the name is displayed.
=== Structure of a utility ROM ===
| &38
| 56
| startup code (?) (extension ROM has &c9). This is executed.
|-
| &70
| 144
| Loading Common code to load files from ROM (note 3)
|-
| &100
2. Accessory ROM name is ASCII string terminated with '$'. Graduate's Accessory ROM 1 is called "CP/M Accessory Rom 1\r\n$". You need to provide a description. At a minimum '$' on it's own is ok. The code displays the string and doesn't check if it goes past the space allocated in the ROM.
3. Loading code is required. A dissassembly is shown below. The ROM executes it. Code is copied from &c070 (length &200) to &3f70 in RAMtherefore copying both the loading code and the directory.
;; HL = address of directory entry
4. Up to 16 files can be defined. Each file takes 1 entry. Unused entries are filled with &FF.
5. Filename is in upper case, 8 characters long, padded with spaces. '.COM' extension is assumed when accessed.
6. ROM starts at &c000. Therefore &c200 is the start of the first file.
[[Category:Operating System]][[Category:CP/M]]
