SC514 is a Z80 CTC card designed for Z50Bus.

The Z80 Counter/Timer Channels (CTC) integrated circuit has four independently programmable counter/timer channels. Each channel can generate a unique mode 2 interrupt.

Each channel’s input and output can be connected in a variety of ways with jumpers. This includes using the Z50Bus USR pins as either input single sources or output signal destinations. It is also possible to cascade channels to create up to a 32-bit counter timer.

The board includes flexible I/O address decoding allowing the CTC’s base address to be on any 4-byte boundary.

The card includes an oscillator making the card’s functionality independent of the main bus clock frequency, thus allowing compatibility of software across different processor speeds.

The main features of this module are:

• Full Z80 mode 2 interrupt support (IEI/IEO daisy-chain)
• Four independent counter/timer channels
• Ability to generate a clock tick interrupt
• On-board clock option to make it independent of the CPU clock
• Interrupt mode 2 converter for up to 4 devices