Trigger
Regular Excitation
Pulses (0 to 127)
Regular Excitation
Pulses (0 to 127)
Extra Excitation
Pulses (0 to 127)
Extra Excitation
Pulses (0 to 127)
High, Low, or Hi-Z
[Pause]
[E-Pulse]
[E-Pulse]
[X-Pulse]
[X-Pulse]
.....
Pause
X-Pulse
E-Pulse
S-Pulse
Trigger and
XMOD = 2, 3
Trigger and
XMOD = 0,1
End of
X-Pulses
End of
E-Pulses and
XMOD= 0,1,2
End of
E-Pulses and
XMOD = 3
Reset
These transitions
cause DMA triggers
End of
S-Pulses
Programmable Pulse Generator (PPG or PPG_A) Block
501
SLAU367P – October 2012 – Revised April 2020
Copyright © 2012–2020, Texas Instruments Incorporated
Sequencer for Acquisition, Programmable Pulse Generator, and Physical
Interface (SAPH, SAPH_A)
generating the pulses. Setting XMOD = 2 must be done when entering the last X-Pulse state. The current
PPG_A state is indicated in SAPH_AXPGCTL.XSTAT Leave at least 6 CPU clocks time margin for
synchronizing. 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 21-8. PPG_A State Diagram for Trill Tone
Figure 21-9. PPG_A Trill Tone Generation With SAPHPGC.PPOL = 1
(Starts With Low Polarity)
21.2.5 Multi Tone Generation
The output pulses consists of multiple phases:
Pause
, a software defined set of
Extra_Excitation
and
Regular_Excitation
phases,
Stop
, and
Pause
again. A state machine in PPG_A controls the flow. Set
SAPH_AXPGCTL.XMOD = 3 like for trill tone generation. When the PPG_A is triggered, it leaves the
Pause phase, generates extra excitation pulses with a frequency defined by
SAPH_AXPGHPER/SAPH_AXPGLPER, then regular excitation pulses with a frequency defined by
SAPH_APGHPER/SAPH_APGLPER. While XMOD = 3 the extra excitation pulses followed by the regular
excitation pulses is repeated. Software is required to change the following:
SAPH_AXPGHPER, SAPH_AXPGLPER, SAPH_AXPGCTL.XPULS,
SAPHPGHPER, SAPHPGLPER, SAPHPGCTL.EPULS, SAPHPGCTL.SPULS,
in a well timed manner. This can be done by direct register access or by DMA accesses.
Finally setting SAPH_AXPGCTL.XMOD = 2 to terminates the multi tone. The last regular excitation pulses
are followed by stop pulses. Then PPG_A goes to Pause phase again (see
and
The stop pulses have a 180° phase shift compared to the last regular excitation pulses. The stop pulses
have same frequency as the last 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.