SC150 – Paged RAM Module (RC2014)

SC150 is a 128k byte paged RAM module designed for the RC2014 bus. It is primarily intended to be used with the paged ROM module (SC151). Together these modules provide suitable memory for running CP/M.



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Parts List

PCB1SC150, v1.0, PCB
C1 to C33Capacitor, ceramic, 100 nF
LED11LED, blue, 3mm
P11Header, male, 1 row x 40 pin, angled
R11Resistor, 1k, 0.25W
U31RAM 128k bytes AS6C1008
U1 socket1Socket, DIP, 14-pin
U2 socket1Socket, DIP, 16-pin
U3 socket1Socket, DIP, 32-pin

Printed Circuit Board

User Guide

SC150 provides 128k of banked RAM together with paging control of the lower 32k. SC151 provides the matching ROM. Together they provide suitable memory for CP/M.

At reset the output bits of integrated circuit U2 are all cleared to zero (low voltage). The ROM is paged into memory from 0x0000 to 0x7FFF (32k bytes) with RAM from 0x8000 to 0xFFFF (32k bytes). When input/output address 0x38 bit 0 is set to one (a high voltage) the ROM is paged out and RAM is paged in, giving a full 64k bytes of RAM from 0x0000 to 0xFFFF.

This module contains 128k bytes of RAM, split into two 64k byte banks. The banks can be swapped with output address 0x30 bit 0. The ROM needs to contain suitable code to swap RAM banks and access them.

The status LED should be ON when the system is in reset. With the recommended firmware, the LED should flash OFF for about half a second when the system is released from reset. It should then turn ON and stay on. User software can then control the LED, as required.

Input/output port functions
I/O Address ReadWrite
(0x08 to 0x0B)
n/aStatus LED
Low = ON, high = OFF
(0x30 to 0x33)
n/aRAM bank select
(0x38 to 0x3B)
n/aMemory paging (lower 32k)
Low = ROM, high = RAM
Jumper options

Assembly Guide

Below is the suggested order of assembly. A general guide to assembling circuit boards can be found here.

  • Resistor R1 (1k)
    This can be fitted either way around
  • Sockets for U1, U2 and U3
    Fit such that the notch in the socket matches the curve in the outline on the PCB silkscreen
  • Bus header P1
    Make sure the pins are parallel to the PCB so that the board is vertical when it is fitted into a backplane socket
  • Decoupling capacitors C1, C2 and C3
    These can be fitted either way around
  • Light emitting diode LED1
    Fit such that the short lead and/or small flat on the plastic is at the end marked with a line on the PCB silkscreen
  • Insert the integrated circuits into their sockets
    Make sure the notch in the component is at the end indicated by the notch in the socket and the curve on the PCB silkscreen


  • This design is made in accordance with the “designed for RC2014” labelling scheme.
  • RC2014 is a trademark of RFC2795 Ltd.
  • This product is designed for hobby use and is not suitable for industrial, commercial, or safety-critical applications.
  • The product contains small parts and is not suitable for young children.

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