SC503 is a Z180 Processor card for Z50Bus.

SC503 includes two 5-volt asynchronous serial ports and an SPI port for connecting a micro SD card adapter.
Hardware features
- 1 x Z180 processor clocked at 18.432 MHz.
- 1 x 512k byte RAM.
- 1 x 512k byte Flash (ROM), typically containing RomWBW.
- 2 x Serial ports, asynchronous, 5-volt, with software selectable baud rates.
- 1 x SPI port, primarily for SD card mass storage.
- 1 x Status LED.
- 1 x 50-pin Z50Bus compatible connector.
- Printed circuit board size 100 mm x 75 mm.
Micro SD Card adapter (shown right) allows a micro SD card to be used for storage of program and data files.

FTDI style 5-volt serial to USB adapter (shown right) allows connection to a computer running a terminal emulation program, such as the Tera Term (free software).
It can also, optionally, supply power to the card.

Software support
- RomWBW, configuration SCZ180_sc500. This configuration supports an SD card for mass storage.
RomWBW is the primary OS for SC503, offering CP/M, SD card, and CF card support (via Z50Bus compatible expansion card).