SC152 is a memory module with 128k bytes of FLASH ROM and 128k pages of RAM designed for the RC2014 bus. This module provides suitable memory for running CP/M.

• SC152 – Assembly Guide
• SC152 – Firmware (SCM S8)
• SC152 – Parts List
• SC152 – Printed Circuit Board
• SC152 – Support
• SC152 – User Guide

Downloads

• SC152, v1.0, Kit contents sheet (PDF)
• SC152, v1.0, Schematic (PDF)
• SC152, v1.0, PCB design files (OSHWLab)
• SC152, v1.0, Gerber files (ZIP)

Suppliers

Kits	Website	Ships from
Stephen C Cousins	Tindie	UK
PCBs	Website	Ships from
Stephen C Cousins	Tindie	UK
Assembled and Tested	Website	Ships from
Not available
Components
See parts list

Parts List

Reference	Qty	Component
PCB	1	SC152, v1.0, PCB
C1 to C4	4	Capacitor, ceramic, 100 nF
JP1+2+3	1	Header, male, 2 row x 10 pin, angled
Jumper	3	Jumper shunt
LED1 and 2	2	LED, green, 3mm, angled
P1	1	Header, male, 2 row x 40 pin, angled (some pins need to be removed)
R1 and R2	2	Resistor, 1k, 0.25W
U1	1	FLASH 128k bytes SST39SF010A
U2	1	RAM 128k bytes AS6C1008
U3	1	74HCT4075
U4	1	74HCT259
IC socket 32-pin U1 and U2	2	Socket, DIP, 32-pin
IC socket 14-pin U3	1	Socket, DIP, 14-pin
IC socket 16-pin U4	1	Socket, DIP, 16-pin

Printed Circuit Board

User Guide

SC152 provides 128k of banked FLASH ROM and 128k bytes of RAM, together with paging control of the lower 32k. This configuration is suitable to run CP/M 2.

At reset the output bits of integrated circuit U4 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.

The 128k bytes of FLASH ROM is split into four 32k byte banks. The bank is selected with JP2 (FLASH address A15) and JP3 (FLASH address A16). By default these jumpers should be set to ‘0’ selecting the lowest 32k bytes. By setting jumpers to either 0 or 1, any of the four banks can be selected. Alternatively, these jumpers can be set for software selection of the bank, using output addresses 0x20 bit 0 and 0x28 bit 0.

The 128k bytes of RAM is split into two 64k byte banks. The bank can be selected with output addresses 0x30 bit 0

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	Read	Write
0x00 (0x00 to 0x03)	n/a	User LED (LED 2) Low = OFF, high = ON
0x08 (0x08 to 0x0B)	n/a	Status LED (LED 1) Low = ON, high = OFF
0x20 (0x20 to 0x23)	n/a	ROM bank select FA15
0x28 (0x28 to 0x2B)	n/a	ROM bank select FA16
0x30 (0x30 to 0x33)	n/a	RAM bank select RA16
0x38 (0x38 to 0x3B)	n/a	Memory paging (lower 32k) Low = ROM, high = RAM

Jumper options

Jumper	Function
JP1	FLASH write enable / protect Read only = Write protected Write = Read and write enabled

It is recommended that a jumper shunt be fitted in the “Read only” position of JP1 during normal use. It only needs to be in the “Write” position when the contents of the FLASH is to be updated. While the FLASH device requires a very specific sequence of events to protect it against accidental modification, it is best to play safe and use the jumper to ensure it can not be written to.

Assembly Guide

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

• Resistors R1 and R2
  These 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
  Some pins need to be pulled out of the second row to match the holes in the PCB. 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, C3 and C4
  These can be fitted either way around
• Light emitting diodes LED1 and LED2
  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
• Header pins JP1, JP2 and JP3
  This can be one header with a few pins pulled out or three separate headers. Fit a jumper shunts in the “Read only” position of JP1 and in position “0” of JP2 and JP3
• 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

Notes

• 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.