DR
CLKR_int
B6
B7
Data hold
Data setup
ÁÁÁÁÁÁÁÁÁ
ÁÁÁÁÁÁÁÁÁ
ÁÁ
ÁÁ
ÁÁ
ÁÁ
Disable time
Propagation
delay
A1
A0
B7
CLKX_int
DX
Architecture
1197
SPRUH82C – April 2013 – Revised September 2016
Copyright © 2013–2016, Texas Instruments Incorporated
Multichannel Buffered Serial Port (McBSP)
On the transmit side, the transmit clock polarity bit, CLKXP, sets the edge used to shift and clock out
transmit data. Data is always transmitted on the rising edge of CLKX_int (see
). If CLKXP = 1
and external clocking is selected (CLKXM = 0 and CLKX is an input), the external falling-edge-triggered
input clock on CLKX is inverted to a rising-edge-triggered clock before being sent to the transmitter. If
CLKXP = 1 and internal clocking is selected (CLKXM = 1 and CLKX is an output pin), the internal (rising-
edge-triggered) clock, CLKX_int, is inverted before being sent out on the CLKX pin.
Similarly, the receiver can reliably sample data that is clocked (by the transmitter) with a rising-edge clock.
The receive clock polarity bit, CLKRP, sets the edge used to sample received data. The receive data is
always sampled on the falling edge of CLKR_int (see
). Therefore, if CLKRP = 1 and external
clocking is selected (CLKRM = 0 and CLKR is an input pin), the external rising-edge triggered input clock
on CLKR is inverted to a falling-edge clock before being sent to the receiver. If CLKRP = 1 and internal
clocking is selected (CLKRM = 1), the internal falling-edge-triggered clock is inverted to a rising edge
before being sent out on the CLKR pin.
In a system where the same clock (internal or external) is used to clock the receiver and transmitter,
CLKRP = CLKXP. The receiver uses the opposite edge as the transmitter to ensure valid setup and hold
times of data around this edge.
shows how data clocked by an external serial device using a
rising-edge clock can be sampled by the McBSP receiver with the falling edge of the same clock.
Figure 25-3. Transmit Data Clocking
Figure 25-4. Receive Data Clocking