Memotech Limited MTX 500 User's Guide download pdf (Page 9)

MEMORY

REMEMOrizer provides :-

 replacement for the 8KB OS ROM

 replacement for the 8KB BASIC ROM

 8KB CP/M boot ROM

 8KB SDX BASIC ROM

 320KB of extra RAM

 128KB virtual cassette tape space

 32KB memory upgrade if attaching REMEMOrizer to an MTX500

 64KB memory upgrade if attaching to MTX with no memory at all

The final bullet point is relevant if the user has tried to upgrade an MTX500, has removed the RAM

and now has a functional MTX with no memory installed.

MTX MEMORY MAPPING

The Z80 is an 8 bit processor with a 16 bit address bus, this allows the processor to directly access a

total of 64K of memory (2^16 bits). The processor also has a separate 64K of addresses for input (I)

and output (O) devices. The addresses and data lines for memory and I/O instructions use the same

physical wiring connections, the Z80 uses different control signals to define when a memory or I/O

operation is being performed. The 64K memory address limit can be extended using a technique

called bank or page switching. The operating system can select which page(s) are addressed at any

given time. On the MTX computer, Output port 0 is the page port which uses the 74LS373 octal latch

in position 5A on the system board :-

Bits D0 to D3 (P0 to P3) define the RAM page address

Bits D4 to D6 (R0 to R2) define the ROM page address

Bit D7 (RELCPM) defines a ROM based system (D7 = 0) or a RAM based system (D7 = 1)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 ... 32 33

No comments

Memotech Limited MTX 500 User's Guide Page 9