SC706 is a Z80 Central Processor Unit (CPU) module with three clock oscillator options, and an optional voltage supervisor and reset device, designed for the RCBus.
- SC706 – Assembly guide
- SC706 – Compatibility
- SC706 – Parts list
- SC706 – Printed circuit board
- SC706 – User guide
- SC700 series information
- SC700 series support
Downloads
- SC706, v1.0, Kit contents sheet (PDF)
- SC706, v1.0, Schematic (PDF)
- SC706, v1.0, PCB design files (OSHWLab)
- SC706, v1.0, Gerber files (ZIP)
Errata
- PCB SC706 v1.0.0 needs a wire link for capacitor C7 if the oscillator X2 is not populated
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 | SC706, v1.0, PCB |
| C1 to C4 | 4 | Capacitor, ceramic, 100 nF |
| C5 and C6 | 2 | Capacitor, ceramic, 22 pF |
| C7 and C8 | 0 | Capacitor, ceramic, ~22 pF Not included in the kit |
| C9 | 1 | Capacitor, ceramic, 1 nF Not included in the kit |
| JP1 | 1 | Header, male, 2 row x 4 pin, angled or male, 2 row x 4 pin, straight Angled pins included in kit |
| JP2 | 1 | Header, male, 1 row x 2 pin, angled or male, 1 row x 2 pin, straight Angled pins included in kit |
| Jumper | 2 | Jumper shunt |
| P1 | 1 | Header, male, 2 row x 40 pin, angled |
| P2 | 1 | Header, male, 1 row x 2 pin, angled or male, 1 row x 2 pin, straight Angled pins included in kit |
| R1 | 1 | Resistor, 1M, 0.25W |
| R2 | 1 | Resistor, 1k, 0.25W |
| R3 | 0 | Resistor, ~1M, 0.25W Not included in the kit |
| R4 | 0 | Resistor, ~1k, 0.25W Not included in the kit |
| R5 to R9 | 5 | Resistor, 10k, 0.25W |
| SW1 | 1 | Switch, tactile button, angled |
| Screw (for spacer) | 1 | Machine screw, 6mm, M3 |
| Spacer | 1 | Spacer, 10mm, M3, nylon |
| U1 | 1 | Z80 CPU, Z84C0008PEG, or Z80 CPU, Z84C0010PEG |
| U2 | 1 | 74HCT04 |
| U3 | 1 | DS1233-5+ supervisor Not included in the kit |
| X1 | 1 | Crystal, 7.3728MHz |
| X2 | 0 | Crystal, typically 2 to 10MHz Not included in the kit |
| X3 | 0 | Oscillator, 8 or 14-pin Not included in the kit |
| IC socket 40-pin U1 | 1 | Socket, DIP, 40 pin |
| IC socket 14-pin U2 | 1 | Socket, DIP, 14-pin |
Printed Circuit Board
Compatibility
This module conforms to the RCBus specification v1.0 for RCBus-2014 and RCBus-Z80.
User Guide
This module conforms to the RCBus specification v1.0 for RCBus-2014 and RCBus-Z80.
SC706 provides a Z80 Central Processor Unit (CPU) module with three clock oscillator options, and an optional voltage supervisor and reset device, designed for the RCBus.
The PCB has three clock oscillators, with the required oscillator selected with a jumper. This allows several different oscillators to be including with easy selection of the desired clock source. The kit includes parts for clock oscillator 1 only (7.3728 MHz). If X2 is not populated, solder a link across C7 so the input to U2 is not left floating. Strange things can happen if it is left floating.
It is also possible to build the PCB without any of the oscillator parts and use a clock source from a different module on the bus. Alternatively, the clock source selection jumper (X1, X2 or X3) can be left off so the onboard oscillator(s) are isolated and not used. This jumper simply connects the required oscillator output to the CPU’s clock input pin.
There is also a jumper to allow the CPU’s clock to be connected to the RCBus CLK signal. This is normally desirable but it can be isolated if required.
If fitted, the voltage supervisor and reset device (U3) provides a reliable power up reset. It works by holding the CPU in reset until the supply voltage reaches approximately 4.75 volts. If the system does not seem to be working, always check the supply voltage is above 4.75 volts on the PCB and that the RESET signal is a logic high voltage, typically above 4 volts. The supervisor should hold the reset low of about 0.5 seconds after the system is turned on and after the reset button is released.
The system should only include one enabled voltage supervisor, so a jumper option has been provided to connect or isolate this device. Normally, it should be connected, but if you have a supervisor on another module you may need to isolate this one.
Input/output port functions
| I/O Address | Read | Write |
| none | n/a | n/a |
Jumper options
| Jumper | Function |
| JP 1 | Clock signals JP1.1 connects CPU clock to Clock X1 JP1.2 connects CPU clock to Clock X2 JP1.3 connects CPU clock to Clock X3 JP1.4 connects Bus clock to CPU clock |
| JP 2 | Enable voltage supervisor |
Clock oscillators X2 and X3 are optional. The default is to connect the output of clock oscillator X1 to the CPU and the RCBus CLK pin. This requires a jumper shunt in each of the two marked default positions (JP1.1 and JP1.4). If you wish to use a clock sourced from a different module then the X1 jumper should be removed.
Fit a jumper shunt to JP2 if the voltage supervisor is to be used. This jumper connects the voltage supervisor to the RESET signal. The system should only contain one enabled supervisor, thus the jumper has been provided to isolate or connect this device.
Assembly Guide
Below is the suggested order of assembly. A general guide to assembling circuit boards can be found here.
The kit does not include parts for the optional oscillators X2 and X3,
- Resistors R1, R2, R5, R6, R7, R8 and R9
These can be fitted either way around - Decoupling capacitors C1, C2, C3 and C4
These can be fitted either way around - Header pins JP2 and P2
This can be a single strip of 5 pins with the middle pin removed - Sockets for U1 and U2
Fit such that the notch in the socket matches the curve in the outline on the PCB silkscreen - Capacitors C5 and C6
These can be fitted either way around - If X2 is not going to be populated, solder a link across C7 so the input to U2 is not left floating. Strange things can happen if it is left floating
- 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
- Crystal X1
This can be fitted either way around - Switch SW1
- Fit a jumper shunts in the default “CPU clock = Clock X1” and “Bus clock = CPU clock” positions of JP1, as indicated on the PCB
- Fit a jumper shunt to JP2 only if you want the voltage supervisor on this board to be enabled. You should only have one voltage supervisor enabled in your system.
- 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
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.
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