SC720 is a Z80 Single Board Computer (SBC) in a motherboard format. It can run RomWBW and the Small Computer Monitor (SCM).
PRE-RELEASE & INCOMPLETE
- SC720 – Assembly guide
- SC720 – Compatibility
- SC720 – Firmware, RomWBW
- SC720 – Firmware, SCM
- SC720 – Parts list
- SC720 – Printed circuit board
- SC720 – User guide
- Designing your RCBus computer
- SC700 series information
- SC700 series support
Downloads
- SC720, v1.0, Kit contents sheet (PDF)
- SC720, v1.0, Schematic (PDF)
- SC720, v1.0, PCB design files (OSHWLab)
- SC720, v1.0, Gerber files (ZIP)
Errata
Nothing known
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
Printed Circuit Board
Compatibility
This module conforms to the RCBus specification v1.0 for RCBus-2014 and RCBus-Z80.
User Guide
SC720 is a Single Board Computer (SBC) meaning it can work without any other backplanes or modules. It is based on a Z80 CPU running at 7.3728 MHz, with 512k bytes of RAM, two 512k byte of FLASH ROMs, a Z80 SIO/2 provides two serial port, a Compact Flash card interface and an output port with eight LEDs.
The kit includes RomWBW pre-programmed into a FLASH ROM. This includes a CP/M and a range of other software.
The kit also includes the Small Computer Monitor pre-programmed into a FLASH ROM. This includes a capable debug/monitor, BASIC, and a CP/M loader.
Input/output port functions
| I/O Address | Read | Write |
| 0x00 (0x00 to 0x03) | n/a | LED port (LED 1 to 8) Low = OFF, high = ON |
| 0x10 (0x10 to 0x17) | Compact Flash Read | Compact Flash Write |
| 0x80 (0x80 to 0x83) | SIO/2 Read | SIO/2 Write |
Z80 SIO/2 register addresses
| I/O Address | Z80 PIO/2 register |
| 0x80 | Port A control |
| 0x81 | Port A data |
| 0x82 | Port B control |
| 0x83 | Port A data |
Jumper options
| Jumper | Function |
| JP 1 | FLASH write enable / protect Read only = Write protected Write = Read and write enabled |
| JP 2 | FLASH ROM select Either U3 or U4 |
| JP 3 | Selects the serial clock source for port A JP 3.1-2 Clock source is bus CLK2 signal JP 3.2-3 Clock source is oscillator X1 The default is X1 |
| JP 4 | Selects the serial clock source for port B JP 4.1-2 Clock source is bus CLK2 signal JP 4.2-3 Clock source is oscillator X1 The default is X1 |
| JP 5 | Connects the bus TX signal to TXA or TXB JP 5.1-2 Connect port A TX signal to bus TX signal JP 5.2-3 Connect port B TX signal to bus TX signal The default is jumper shunt not fitted |
| JP 6 | Connects the bus RX signal to RXA or RXB JP 6.1-2 Connect port A RX signal to bus RX signal JP 6.2-3 Connect port B RX signal to bus RX signal The default is jumper shunt not fitted |
| JP 7 | Connects the bus TX2 signal to TXB or /RTSA JP 7.1-2 Connect port B TX signal to bus TX2 signal JP 7.2-3 Connect port A /RTS signal to bus TX2 signal The default is jumper shunt not fitted |
| JP 8 | Connects the bus RX2 signal to RXB or /CTSA JP 8.1-2 Connect port B RX signal to bus RX2 signal JP 8.2-3 Connect port A /CTS signal to bus RX2 signal The default is jumper shunt not fitted |
| JP 9 | Connects 5 volt power to serial port A connectors The default is jumper shunt not fitted |
| JP 10 | Connects 5 volt power to serial port B connectors The default is jumper shunt not fitted |
| JP 11 | JP 11.1 Connect P37 signal between bus sockets JP 11.2 Connect P38 signal between bus sockets* JP 113 Connect P39 signal between bus sockets* * See daisy chain details below |
| JP 12 | JPx.1 Connect P42 signal between bus sockets* JPx.2 Connect P43 signal between bus sockets* JPx.3 Connect P44 signal between bus sockets * See daisy chain details below |
| JP 13 | Connects bus IEO signal to SIO/2 IEO signal The default is jumper shunt not fitted |
JP 11 and JP 12 allow some signals to be isolated between bus sockets. Also, jumpers allow daisy chains to be created. See backplanes, such as SC701, for details jumper positions).
Assembly Guide
Below is the suggested order of assembly. A general guide to assembling circuit boards can be found here.
TODO
- Header socket P2
This should lay flat against the PCB - Resistors R1 to R7
These can be fitted either way around - Decoupling capacitors C1 to C6
These can be fitted either way around - Sockets for U1 to U5
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 - Header pins P3
Ensure the pins are parallel to socket P2 - 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 - Reset switch SW1
- Oscillator X1
Ensure the orientation matches the PCB silkscreen, noting the sharp corner at pins 1 - 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.
Small Computer Central 