SC606 is a DS1302 based real time clock designed for the 40-pin RCBus.

• SC606 – Assembly guide
• SC606 – Compatibility
• SC606 – Parts list
• SC606 – Printed circuit board
• SC606 – User guide
• SC600 series information
• SC600 series support

Downloads

• SC606, v1.0, Kit contents sheet (PDF)
• SC606, v1.0, Schematic (PDF)
• SC606, v1.0, PCB design files (OSHWLab)
• SC606, v1.0, Gerber files (ZIP)

Errata

• Nothing known

Suppliers

Kits	Website	From	Currency
Small Computers Direct	SCDirect	UK	GBP
Stephen C Cousins	Tindie	UK	USD
Small Computer Central	Lectronz	UK	Euro/USD
PCBs	Website	From	Currency
Small Computers Direct	SCDirect	UK	GBP
Stephen C Cousins	Tindie	UK	USD
Small Computer Central	Lectronz	UK	Euro/USD
Assembled and Tested	Website	From	Currency
Not available
Components
See parts list

Parts List

Reference	Qty	Component
PCB	1	SC606, v1.0, PCB
B1	1	Battery holder CR2032 Battery not included in the kit
C1 to C5	5	Capacitor, ceramic, 100 nF
JP1	1	Header, male, 2 row x 8 pin, angled or straight ?
Jumpers	8	Jumper shunt
P1	1	Header, male, 1 row x 40 pin, angled
P2	1	Header, male, 1 row x 10 pin, angled
R1 and R2	2	Resistor, 10k, 0.25W
RN1	1	Resistor network, 8x100k, SIL, 9-pin
Screw (for spacer)	1	Machine screw, 6mm, M3
Spacer	1	Spacer, 10mm, M3, nylon
U1	1	74HCT688
U2	1	74HCT273
U3	1	74HCT125
U4	1	74HCT32
U5	1	DS1302+
X1	1	Crystal, 32.768 kHz, 6pF
IC socket 20-pin U1 and U2	2	Socket, DIP, 20-pin
IC socket 14-pin U3 and U4	2	Socket, DIP, 14-pin
IC socket 8-pin U5	1	8-pin PDIP socket

Printed Circuit Board

User Guide

SC606 includes a real time clock based on a DS1302+ integrated circuit. Several spare I/O bits are also available for user functions. Support for the real time clock is included in RomWBW but not in plain CP/M 2.2 or in the Small Computer Monitor.

The module’s I/O address is set with jumpers (JP1). Check the requirements of the software you intend to use. Fit a jumper shunt in each position where the corresponding address bit is to be a ‘1’ (high).

Header pins P2 provide access to spare I/O bits not used for the real time clock. The input bits can be used without restrictions but outputting values to the output bits must be done with care as the port is shared with the real time clock output bits.

Input/output port functions

RCBus I/O Address	Read	Write
Configurable *1 base address	Inputs	Outputs
Bit 0	RTC serial data	Output bit 0
Bit 1	Undefined	Output bit 1
Bit 2	Undefined	Output bit 2
Bit 3	Undefined	Output bit 3
Bit 4	Input bit 4	RTC chip enable (lo)
Bit 5	Input bit 5	RTC write enable (lo)
Bit 6	Undefined	RTC serial clock
Bit 7	Undefined	RTC serial data

The RCBus I/O base address should be set to match the software you are using. Typically, this is 0x0C or 0xC0.

Jumper options

Jumper	Function
JP1	Set module’s RCBus I/O address

Connectors

Connector	Function
P1	RCBus connector
P2	Digital I/O Pin 1 = 5 volts output Pin 2 = Output bit 0 Pin 3 = Output bit 1 Pin 4 = Ground (0 volts) Pin 5 = Output bit 2 Pin 6 = Output bit 3 Pin 7 = 5 volts output Pin 8 = Input bit 4 Pin 9 = Inpit bit 5 Pin 10 = Ground (0 volts)

Assembly Guide

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

1. Resistors R1 and R2
   These can be fitted either way around
2. Crystal X1
   These can be fitted either way around
   The crystal can be held firmly in place with a piece of wire, such as an off-cut of resistor or capacitor leg, fitted through the holes provided
3. Decoupling capacitors C1 to C5 (100nF)
   These can be fitted either way around
4. Bus header P1 (1 row x 40 pin, angled)
   Make sure the pins are parallel to the PCB so that the board is vertical when it is fitted into a backplane socket
5. Header pins P2 (1 row x 10 pin, angled)
6. Sockets for U1 to U5
   Fit such that the notch in the socket matches the curve in the outline on the PCB silkscreen
7. Resistor networks RN1
   These must be fitted the correct way around whereby the dot on the component matches the dot on the PCB silkscreen
8. Header pins JP1
9. Battery holder B1
10. 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
11. Fit a CR2032 battery into the battery holder
    The module can be used with or without a battery but without the battery the time is not maintained when the main power is off
12. Fit the nylon spacer in the mounting hole

Fit jumper shunts to select the required I/O address. The two most commonly used addresses are illustrated below. Check the needs of the software you intend using.

Compatibility

This module conforms to the RCBus specification v1.0 for RCBus-2014 (40-pin bus) and RCBus-Z80 (40-pin bus).

The RCBus specification includes RCBus-2014 (both RC2014 standard 40-pin bus and RC2014 enhanced 60-pin bus) and also the full 80-pin RCBus. The 80-pin RCBus provides support for advanced Z80 features, such as the interrupt daisy-chain, as well as support for other processor families.

Backplane	?	Compatibility notes
RCBus 80-pin		Fully supported
RCBus 60-pin (RC2014 enhanced)		Fully supported
RCBus 40-pin (RC2014 standard)		Fully supported

Notes

• 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.
• RomWBW is copyright Wayne Warthen and has been provided free of charge with his permission.
• RC2014 is a trademark of RFC2795 Ltd.