Changes

Broadly speaking, the Machine Pack is reponsible for the control of hardware peripherals, but it will be convenient to include the main initialisation processes under this heading, since they are largely concerned with peripheral setting-up.

Several of the Machine Pack routines depend on the action of other routines to set up data. To understand this data in full, you need to read 'The Ins and Outs of the AMSTRAD CPC464', which gives full details of the peripheral codes. Only the more essential codes will be defined here.

At switch—on, or in response to instruction code &C7, location 0000 is entered. At switch-on, lower ROM is enabled, but the ROM routines are later copied to the corresponding RAM locations in this area, so the enable state of the lower ROM is then unimportant. However, the first action of the reset routine is to output &89 to the Video Gate array on I/0 address 7FXX, and this enables lower ROM, disables upper ROM, and also sets up Mode 1. There being no further room in the RST Area the routine jumps to 0580 to continue reset action.