Architecture
1543
SPRUH82C – April 2013 – Revised September 2016
Copyright © 2013–2016, Texas Instruments Incorporated
Universal Parallel Port (uPP)
32.2.5 Protocol Description
The uPP peripheral consists of two independent channels, each possessing its own data lines and control
signals. A channel may be configured to run in transmit or receive mode and to use either 8 or 16 data
lines (8-bit or 16-bit mode) using the uPP channel control register (UPCTL). A channel may also be
configured to ignore certain control signals using the uPP interface configuration register (UPICR). Each
uPP defaults to 8-bit mode and uses all four control signals, unless otherwise configured.
summarizes the signals that are required for basic operation in receive and transmit modes. The following
subsections describe the role of each signal.
Table 32-5. Required Signals for Various Modes
Signal Required?
Signal Name
Transmit Mode
Receive Mode
DATA[7:0]
√
√
DATA[15:8]
START
√
ENABLE
√
WAIT
√
CLOCK
√
√
32.2.5.1 DATA[7:0] Signals
In 8-bit mode, DATA[7:0] comprise the channel’s entire data bus. In 16-bit mode, DATA[7:0] comprise the
least-significant bits of the 16-bit word. The channel’s data width is selected using the IWx bit in UPCTL.
In transmit mode, these pins are outputs that transmit data supplied by the channel’s associated DMA
channel. While the channel is idle, their behavior depends on the TRISx bit in UPICR. These pins can be
configured to drive an idle value (TRISx = 0, VALx field in the uPP interface idle value register (UPIVR)) or
be in a high-impedance state while idle (TRISx = 1).
In receive mode, these pins are inputs that provide data to the channel’s associated DMA channel.
Note that the DATA signals map differently to the DATA and XDATA pins for various uPP configurations,
see
for more information.
32.2.5.2 DATA[15:8] Signals
In 8-bit mode, DATA[15:8] are not used. In 16-bit mode, DATA[15:8] comprise the most-significant bits of
the 16-bit word. The channel’s data width is selected using the IWx bit in UPCTL. A channel may be
further configured to use only part of its DATA[15:8] pins, which allows any total data width from 8 to 16
bits.
describes data format and packing in the 9-bit to 15-bit configurations.
While in use, the direction and behavior of DATA[15:8] in transmit and receive modes are the same as the
direction and behavior of DATA[7:0].
Note that the DATA signals map differently to the DATA and XDATA pins for various uPP configurations,
see
for more information.
32.2.5.3 START Signal
The uPP transmitter asserts the START signal when it transfers the first word of a data line. A line is
defined in terms of the channel’s associated DMA channel; for more on DMA programming concepts, see
. The START signal is active-high by default, but its polarity is controlled by the
STARTPOLx bit in UPICR.
In transmit mode, START is an output signal and is always driven; in receive mode, START is an input
signal and may be disabled using the STARTx bit in UPICR.