15.6.3 Bits Used to Enable and Configure the Clock Stop Mode
The bits required to configure the McBSP as an SPI device are introduced in
shows
how the various combinations of the CLKSTP bit and the polarity bits CLKXP and CLKRP create four possible
clock stop mode configurations. The timing diagrams in
show the effects of CLKSTP, CLKXP, and
CLKRP.
Table 15-14. Bits Used to Enable and Configure the Clock Stop Mode
Bit Field
Description
CLKSTP bits of SPCR1
Use these bits to enable the clock stop mode and to select one of two timing variations. (See also
CLKXP bit of PCR
This bit determines the polarity of the CLKX signal. (See also
.)
CLKRP bit of PCR
This bit determines the polarity of the MCLKR signal. (See also
CLKXM bit of PCR
This bit determines whether CLKX is an input signal (McBSP as slave) or an output signal (McBSP as master).
XPHASE bit of XCR2
You must use a single-phase transmit frame (XPHASE = 0).
RPHASE bit of RCR2
You must use a single-phase receive frame (RPHASE = 0).
XFRLEN1 bits of XCR1
You must use a transmit frame length of 1 serial word (XFRLEN1 = 0).
RFRLEN1 bits of RCR1
You must use a receive frame length of 1 serial word (RFRLEN1 = 0).
XWDLEN1 bits of XCR1
The XWDLEN1 bits determine the transmit packet length. XWDLEN1 must be equal to RWDLEN1 because in
the clock stop mode. The McBSP transmit and receive circuits are synchronized to a single clock.
RWDLEN1 bits of RCR1
The RWDLEN1 bits determine the receive packet length. RWDLEN1 must be equal to XWDLEN1 because in
the clock stop mode. The McBSP transmit and receive circuits are synchronized to a single clock.
Table 15-15. Effects of CLKSTP, CLKXP, and CLKRP on the Clock Scheme
Bit Settings
Clock Scheme
CLKSTP = 00b or 01b
Clock stop mode disabled. Clock enabled for non-SPI mode.
CLKXP = 0 or 1
CLKRP = 0 or 1
CLKSTP = 10b
Low inactive state without delay: The McBSP transmits data on the rising edge of CLKX and receives data on
the falling edge of MCLKR.
CLKXP = 0
CLKRP = 0
CLKSTP = 11b
Low inactive state with delay: The McBSP transmits data one-half cycle ahead of the rising edge of CLKX and
receives data on the rising edge of MCLKR.
CLKXP = 0
CLKRP = 1
CLKSTP = 10b
High inactive state without delay: The McBSP transmits data on the falling edge of CLKX and receives data on
the rising edge of MCLKR.
CLKXP = 1
CLKRP = 0
CLKSTP = 11b
High inactive state with delay: The McBSP transmits data one-half cycle ahead of the falling edge of CLKX and
receives data on the falling edge of MCLKR.
CLKXP = 1
CLKRP = 1
Multichannel Buffered Serial Port (McBSP)
SPRUH18I – JANUARY 2011 – REVISED JUNE 2022
TMS320x2806x Microcontrollers
913
Copyright © 2022 Texas Instruments Incorporated
Содержание TMS320 2806 Series
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