Dk'tronics memory expansion

RAM Memory Expansions by Dk'tronics.

Description

Dk'tronics produced 2 different memory expansions, a 64K and a 256K which were compatible with all (non Plus) CPCs. The expansions meant that CP/M Plus and CP/M 2.2 (with the use of a utility supplied) could both access a 'massive' 61K TPA. The available memory could be switched in and out of the Z80 64K address block in banks of 16K using either RSX (bar) commands within basic or within an assembly code program.

The additional bar commands were:

|Bank, n - Map a 16K bank directly into memory space (where n is the bank No.)
|Swap - Alternate between high and low screens
|Low - Change to the low screen
|High - Change to the high (default) screen
|Saves, n - Store a screen to a 16K bank (where n is the bank No.)
|Loads, n - Retrieve a screen from a 16K bank (where n is the bank No.)
|Savew, w, n - Stores a windows contents into a 16K bank (where n is the bank No.)
|Loadw, w, n - Load a window with the data from a 16K bank (where n is the bank No.)
|Saved, n, s, l - Transfer original RAM to expansion RAM
|Loadd, n, s, l - Load original RAM from expansion RAM
|Peek, n, s, v - Read the value of a byte in the expansion RAM
|Poke, n, s, v - Write to a byte in the expansion RAM

A further command which was considered to be only for 'advanced' users was also described later in the handbook. The command |Askram, E, V (E=enquiry No. V=variable) could be used to request information from the expansion card, including the amount of RAM available (where E=1), return the number of banks available (where E=2) or (E=3) returned a 0 or 1 to indicate whether the expansion card 'had a problem'.