What is it?
A Memory Module designed for the RC2014 computer system. It provides 32kB of ROM (EEPROM) and 128kB of paged RAM, on a simple, robust, and cost effective 4 layer PCB.
Why did you make it?…
A Memory Module designed for the RC2014 computer system. It provides 32kB of ROM (EEPROM) and 128kB of paged RAM, on a simple, robust, and cost effective 4 layer PCB.
Why did you make it?
To provide a very simple, cost effective Memory Module for the RC2014 system. It provides memory support for all the major RC2014 firmware options, without unnecessary jumpering complexity. This includes 32kB NASCOM Microsoft Basic, CP/M by Grant Searle (distributed with the RC2014 Pro), and the CP/M-IDE.
Microsoft BASIC, for 32k RAM, 68B50 ACIA, with origin 0x0000.
Microsoft BASIC, for 32k RAM, SIO/2, with origin 0x0000.
CP/M Monitor, for pageable ROM, 64k RAM, 68B50 ACIA, CF Module at 0x10, with origin at 0x0000.
CP/M Monitor, for pageable ROM, 64k RAM, SIO/2, CF Module at 0x10, with origin at 0x0000.
Small Computer Monitor for pageable ROM, 64k RAM, SIO/2 or 68B50 ACIA, with Microsoft BASIC and CP/M boot options.
Small Computer Monitor for any ROM, any RAM, any USART.
It is designed to be the simplest (no jumpers, no configurations), lowest cost (4 ICs only), integrated memory subsystem to be used with the RC2014 in its simpler versions (Classic II, Micro, Pro). It is functionally equivalent to the Pageable ROM Module and the 64k RAM Module, but it also provides an additional 64kB of RAM in a second page.
When used with CP/M and the standard Backplane 8, it provides a small advantage over separate ROM and RAM boards in that you don't need a separate flying /PAGE wire. That's very convenient.
Space is provided for a Zero Insertion Force (ZIF) socket for the EEPROM, to support rapid development cycles by rewriting of the EEPROM using an external programmer.
The Memory Module provides 32kB of ROM at address 0x0000 that can be paged out by writing to I/O address 0x38. Leaving two pages of 64kB of RAM, that can be paged by writing to I/O address 0x30.
A similar page switching circuit is used for the memory subsystem in the SC108, SC114, and PickledDog RAM/ROM products.
Support is available in z88dk for reading and writing the second page of RAM, making the additional 64kB of RAM (less 32 Byte RAM copy stub) available to your C or Z80 assembly programs.
Either 256kb (32kB) or 512kb (64kB) EEPROM can be used, of type AT27C256R, SST27SF256, W27C512, or other variants. Where a Winbond W27C512 64kB device is selected the 32kB image must be written into the upper 32kB of the device memory addressing, starting from 0x8000 through to 0xFFFF, which will be read from memory address 0x0000. The lower 32kB of the W27C512 EEPROM device cannot be read using this Memory Module, as Pin 1 (A15) is held at VCC/VPP, to support the AT27C256R PROM and SST27SF256 EEPROM devices.
Ordering Options
This is the Memory Module Printed Circuit Board (PCB) Only.
If the postage is too high, then please use the attached documentation to make your own, and share with others.
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