Freescale Semiconductor PowerQUICC MPC885 Reference Manual page 916

Parallel Interface Port (PIP)
The following is a list of the PIP controller's Centronics-compatible features:
• Superset of the Centronics standard
• Supports Centronics-type transmitter and receiver operating modes
• Supports bidirectional Centronics
• Message-oriented data structure flexibility
• Flexible receive control character comparison
• Flexible timing modes with programmable timing parameters
Figure 33-20 shows the signals needed to implement a standard Centronics interface.
Data
STB
BUSY
ACK
SELECT
PERROR
FAULT
The following subsections describe the PIP configured as a Centronics interface.
33.9.1 PIP as a Centronics Transmitter
Once the TxBDs are prepared and PIPC[STR] is set, the PIP processes the next ready BD in the TxBD
table. When configured for a Centronics interface, the PIP transmitter fetches data from memory and starts
sending to the printer. Assuming the corresponding status mask bits are set in SMASK, the PIP transmitter
checks the printer status lines (SELECT, PERROR and FAULT) for Tx errors before each transfer.
Configure PB30, PB29, and PB28 as general-purpose inputs and connect them to SELECT, PERROR, and
FAULT, respectively.
For each transfer, the PIP drives the data on the Centronics interface data lines and generates a strobe pulse,
assuming the previous data has been acknowledged and the minimum setup time requirement is met.
Strobe pulse width and setup time parameters are set in the PIP timing parameters register (PTPR). Note
that one data frame can span several buffers with a maskable interrupt generated after each BD is
processed.
33-20
Figure 33-20. The PIP Centronics Interface Signals
MPC885 PowerQUICC Family Reference Manual, Rev. 2
Freescale Semiconductor