Functional Description
Parallel Port Interface
The PCCchip2 provides an 8-bit bidirectional parallel port. All eight bits of the port must be either inputs or outputs (no individual selection). In addition to the 8 bits of data, there are two control pins and five status pins. Each of the status pins can generate an interrupt to the MPU in any of the following programmable conditions:
❏High level
❏Low level
❏High-to-low transition
❏Low-to-high transition
This port may be used as a Centronics- compatible parallel printer port or as a general parallel I/O port.
When used as a parallel printer port, the five status pins function as Printer:
❏Acknowledge (ACK)
❏Fault (FAULT*)
❏Busy (BSY)
❏Select (SELECT)
❏Paper Error (PE) The control pins act as:
❏Printer Strobe (STROBE*)
❏Input Prime (INP*)
The PCCchip2 provides an auto-strobe feature similar to that of the MVME147 PCC. In auto-strobe mode, after a write to the Printer Data Register, the PCCchip2 automatically asserts the STROBE* pin for a selected time specified by the Printer Fast Strobe control bit. In manual mode, the Printer Strobe control bit directly controls the state of the STROBE* pin.