user manual

Functional Description
4-14
4
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.