SLAU367P October 2012 – April 2020 MSP430FR5041 , MSP430FR5043 , MSP430FR50431 , MSP430FR5847 , MSP430FR58471 , MSP430FR5848 , MSP430FR5849 , MSP430FR5857 , MSP430FR5858 , MSP430FR5859 , MSP430FR5867 , MSP430FR58671 , MSP430FR5868 , MSP430FR5869 , MSP430FR5870 , MSP430FR5872 , MSP430FR58721 , MSP430FR5887 , MSP430FR5888 , MSP430FR5889 , MSP430FR58891 , MSP430FR5922 , MSP430FR59221 , MSP430FR5947 , MSP430FR59471 , MSP430FR5948 , MSP430FR5949 , MSP430FR5957 , MSP430FR5958 , MSP430FR5959 , MSP430FR5962 , MSP430FR5964 , MSP430FR5967 , MSP430FR5968 , MSP430FR5969 , MSP430FR5969-SP , MSP430FR59691 , MSP430FR5970 , MSP430FR5972 , MSP430FR59721 , MSP430FR5986 , MSP430FR5987 , MSP430FR5988 , MSP430FR5989 , MSP430FR5989-EP , MSP430FR59891 , MSP430FR5992 , MSP430FR5994 , MSP430FR59941 , MSP430FR6005 , MSP430FR6007 , MSP430FR6035 , MSP430FR6037 , MSP430FR60371 , MSP430FR6041 , MSP430FR6043 , MSP430FR60431 , MSP430FR6045 , MSP430FR6047 , MSP430FR60471 , MSP430FR6820 , MSP430FR6822 , MSP430FR68221 , MSP430FR6870 , MSP430FR6872 , MSP430FR68721 , MSP430FR6877 , MSP430FR6879 , MSP430FR68791 , MSP430FR6887 , MSP430FR6888 , MSP430FR6889 , MSP430FR68891 , MSP430FR6920 , MSP430FR6922 , MSP430FR69221 , MSP430FR6927 , MSP430FR69271 , MSP430FR6928 , MSP430FR6970 , MSP430FR6972 , MSP430FR69721 , MSP430FR6977 , MSP430FR6979 , MSP430FR69791 , MSP430FR6987 , MSP430FR6988 , MSP430FR6989 , MSP430FR69891
21.2.3 Dual Tone Generation
The output pulses consists of fife different phases: Pause, Extra_Excitation, Regular_Excitation, Stop, and Pause again. A state machine in PPG_A controls the flow. Set SAPH_AXPGCTL.XMOD = 2 for dual tone generation. When the PPG_A is triggered, it leaves the Pause phase, generates excitation pulses with a frequency defined by SAPH_AXPGHPER/SAPH_AXPGLPER, then excitation pulses with a frequency defined by SAPH_APGHPER/SAPH_APGLPER followed by stop pulses, then goes to Pause phase again (see Figure 21-6 and Figure 21-7). The stop pulses have a 180° phase shift compared to the regular excitation pulses. The stop pulses have same frequency as the regular excitation pulses. The PPG generates up to 127 extra excitation pulses, up to 127 regular excitation pulses and up to 15 stop pulses, which are controlled by the SAPH_AXPGCTL.XPULS, SAPH_APGC.EPULS and SAPH_APGC.SPULS bits, respectively. The pulse polarity is programmable in the SAPH_APGC.PPOL bit. The signal polarity of Pause can be programmed to be logical high, logical low, or high impedance through the SAPH_APGC.PLEV and SAPH_APGC.PHIZ bits.
The PPG_A can be triggered by writing 1 to the SAPH_APPGTRIG.PPGTRIG bit when SAPH_APGCTL.TRSEL = 0 (register mode) or by the acquisition sequencer (ASQ) when SAPH_APGCTL.TRSEL = 1 (auto mode). To avoid unintended pulse outputs, keep SAPH_APGCTL.PPGEN = 0 while updating the PPG_A registers. After the PPG_A registers are updated, write 1 to the SAPH_APGCTL.PPGEN bit before triggering the PPG_A. The SAPH_APGCTL.PPGEN bit must be set before triggering the PPG_A. The output channel is determined by the SAPH_APGCTL.PPGCHSEL bit when SAPH_APGCTL.PGSEL = 0 (register mode) or by the acquisition sequencer (ASQ) when SAPH_APGCTL.PGSEL = 1 (auto mode). Another layer of output control is inside the PHY, so both blocks must be configured properly (see Section 21.3). The PPG_A automatically stops when it completes generating the pulses. To stop generating pulses before completion, regardless of operation mode, write 1 to SAPH_APGCTL.STOP. The PPG_A immediately stops generating pulses. The SAPH_APGCTL.STOP bit is automatically cleared to zero.
Figure 21-6 PPG_A State Diagram for Dual Tone 
Figure 21-7 PPG_A Dual Tone Generation With SAPHPGC.PPOL = 1
(Starts With Low Polarity)