HD68230

HD68230---------------- PitT (Parallel Interface Timer) The HD68230 Parallel Interface/Timer provides versatile double buffered parallel interfaces and an operating system oriented timer to HD68000 systems. The parallel interfaces operate in unidirectional or bidirectional modes, either 8 or 16 bits wide. In the unidirectional modes, an associated data direction register determines whether the port pins are inputs or outputs. In the bidirectional modes the data direction registers are ignored and the direction is determined dynamically by the state of four handshake pins. These programmable handshake pins provide an interface flexible enough for connection to a wide variety of low, medium, or high speed peripherals or other computer systems. The PI/T ports allow use of vectored or autovectored interrupts, and also provide a DMA Request pin for connection to the HD68450 Direct Memory Access Controller or a similar circuit. The PI/T timer contains a 24-bit wide counter and a 5-bit presc...