SC719 is a digital input/output module designed for the RCBus. It offers 8 inputs and 8 outputs at 5-volt TTL levels. Each input and output has an LED to indicate its state.
- SC719 – Assembly guide
- SC719 – Compatibility
- SC719 – Parts list
- SC719 – Printed circuit board
- SC719 – User guide
- SC700 series information
- SC700 series support
Downloads
- SC719, v1.0, Kit contents sheet (PDF)
- SC719, v1.0, Schematic (PDF)
- SC719, v1.0, PCB design files (OSHWLab)
- SC719, v1.0, Gerber files (ZIP)
Errata
- PCB v1.0.0 does not leave enough space for this capacitor C5 to fit tight to the PCB. Fixed in PCB v1.0.1
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 |
Tindie does not collect VAT for EU countries
Lectronz does collect EU VAT for orders up to 150 EUR
Parts List
| Reference | Qty | Component |
| PCB | 1 | SC719, v1.0, PCB |
| C1 to C4 | 4 | Capacitor, ceramic, 100 nF |
| C5 | 1 | Capacitor, electrolytic, 100 µF |
| JP1 | 1 | Header, male, 2 row x 8 pin, angled |
| Jumper | 8 | Jumper shunt |
| LED1 to 8 | 8 | LED, green, 3mm, angled |
| LED9 to 16 | 8 | LED, red, 3mm, angled |
| P1 | 1 | Header, male, 2 row x 40 pin, angled |
| P2 | 1 | Box header, 2 x 10 pin, angled, or Header, male, 2 x 10 pin, angled |
| RN1 | 1 | Resistor network, 8x100k, SIL, 9-pin |
| RN2 and RN3 | 2 | Resistor network, 8x1k, SIL, 9-pin |
| Screw (for spacer) | 1 | Machine screw, 6mm, M3 |
| Spacer | 1 | Spacer, 10mm, M3, nylon |
| U1 | 1 | 74HCT688 |
| U2 | 1 | 74HCT32 |
| U3 | 1 | 74HCT245 |
| U4 | 1 | 74HCT273 |
| IC socket 20-pin U1, U3 and U4 | 3 | Socket, DIP, 20-pin |
| IC socket 14-pin U2 | 1 | Socket, DIP, 14-pin |
Printed Circuit Board
User Guide
SC719 is a digital input/output module designed for the RCBus. It offers 8 inputs and 8 outputs at 5-volt TTL levels. Each input and output has an LED to indicate its state.
The module’s I/O address is set with jumpers (JP1). The module responds to input/output addresses matching the address set with these jumpers. When a jumper shunt is fitted, that bit must be a 1 (high voltage). When the shunt is not fitted, that bit must be a 0 (low voltage). The card has tight address decoding and only occupies a single input/output port address. Typically, the address will be 0x00 which is selected by not fitting any jumper shunts to JP1.
Input/output port functions
| I/O Address | Read | Write |
| Configurable *1 base address | Inputs | Outputs |
The RCBus I/O base address should be set to match the software you are using. Typically, this is 0x00 (no jumper shunts fitted).
Jumper options
| Jumper | Function |
| JP1 | Set module’s RCBus I/O address |
Assembly Guide
Below is the suggested order of assembly. A general guide to assembling circuit boards can be found here.
- Decoupling capacitors C1 to C4
These can be fitted either way around - Sockets for U1 to U4
Fit such that the notch in the socket matches the curve in the outline on the PCB silkscreen - Resistor networks RN1, RN2 and RN3
These must be fitted the correct way around whereby the dot on the component matches the dot 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 - Header pins JP1
- Light emitting diodes LED1 to LED16
The angled LEDs in the kit only fit one way around, but standard LEDs need to have the short lead in the hole marked with a flat line - Box header or header pins P2
- Capacitor C5
PCB v1.0.0 does not leave enough room for this capacitor to fit tight to the PCB - 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 - Fit the nylon spacer in the mounting hole
Compatibility
This module conforms to the RCBus specification v1.0 for RCBus-2014 and RCBus-Z80.
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.
The table below indicates electrical compatibility with each backplane type (40, 60 and 80 pin)
| 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.
Small Computer Central 