Architecture
1539
SPRUH82C – April 2013 – Revised September 2016
Copyright © 2013–2016, Texas Instruments Incorporated
Universal Parallel Port (uPP)
32.2.1.3 Double Data Rate
The uPP peripheral supports two I/O clocking schemes. The first, single data rate (SDR), clocks data from
the DATA pins on either the rising edge or the falling edge (depending on UPICR.CLKINV
n
) of the I/O
clock.
The second clocking scheme is double data rate (DDR). In this mode, data is clocked on both the rising
and falling edges of the I/O clock. However, DDR mode imposes a lower I/O clock speed limit of one
eighth (1/8) the device CPU clock for both transmit and receive modes. The operating speed for transmit
mode with various divisors in each data rate are summarized in
(in this table, a data word is
defined as the data represented on the DATA pins; uPP supports data words in the 8-bit to 16-bit range).
In receive mode, a channel I/O clock is generated by an external source, but the same speed limit applies.
Table 32-1. I/O Clock Speeds for Channel in Transmit Mode Given 150 MHz Transmit Clock
Word Rate (Mw/s)
UPICR.CLKDIVn
I/O Clock (MHz)
Single Data Rate
Double Data Rate
0
75.00
75.00
...
1
37.50
37.50
75.00
2
25.00
25.00
50.00
3
18.75
18.75
37.50
...
...
...
...
15
4.69
4.69
9.38
Additional restrictions may apply, check the device datasheet to see if your particular uPP peripheral has
any additional clock requirements.
32.2.2 Signal Description
Each uPP channel has its own set of control and data signals.
lists every signal and briefly
describes their functions.
explains the uPP protocol.
(1)
This clock can only be used in transmit mode, and must be twice the speed of your desired I/O clock. See
and
the
Device Clocking
chapter for more information.
Table 32-2. uPP Signal Descriptions
Signal
I/O Channel
Type
(Transmit)
Type
(Receive)
Description
DATA[15:0]
—
Output
Input
Parallel data bus
XDATA[15:0]
—
Output
Input
Extended parallel data bus
CHA_START
A
Output
Input
Indicates first data word per line of data
CHA_ENABLE
A
Output
Input
Indicates data transmission active
CHA_WAIT
A
Input
Output
Requests transmitter halt temporarily
CHA_CLOCK
A
Output
Input
Source-synchronous clock signal
CHB_START
B
Output
Input
Indicates first data word per line of data
CHB_ENABLE
B
Output
Input
Indicates data transmission active
CHB_WAIT
B
Input
Output
Requests transmitter halt temporarily
CHB_CLOCK
B
Output
Input
Source-synchronous clock signal
UPP_2xTXCLK
—
Input
—
Optional external source for transmit clock
(1)
Note that the DATA and XDATA pins are not dedicated to a single I/O channel in the same way as the
control signals. For practical reasons, uPP data pin channel assignments are not static. Instead, the data
pins used by each I/O channel (A, B) depend on the operating mode of the uPP peripheral.
summarizes the assignment of the DATA and XDATA pins to each channel for various operating modes,
along with the relevant register settings. For more information on these pins, see your device-specific data
manual.