Operation of the USS Module
455
SLAU367P – October 2012 – Revised April 2020
Copyright © 2012–2020, Texas Instruments Incorporated
Ultrasonic Sensing Solution (USS, USS_A)
1. Applied desired configurations to USS registers (all submodules). Make sure to apply the auto mode
(see
).
2. Set the following bits to 1: SAPHPGCTL.PPGEN, SAPHASCTL0.ASQTEN, SAPHMCNF.LPBE and
SDHSCTL3.TRIGEN
3. Assert the USS_PWRREQ signal (see
).
Table 18-3. USS_PWRREQ Signal Source
UUPSCTL.USSPWRUPSEL
Selected Trigger Source
Comment
0
UUPSCTL.USSPWRUP = 1
Default, write only
1
Internal signal
See device-specific data sheet.
2
Internal signal
See device-specific data sheet.
3
Internal signal
See device-specific data sheet.
18.2.2 Control Signals
Start-up signal, USS_PWRREQ
USS_PWRREQ = 0
→
1 is the signal that powers up the USS module and starts a new measurement. If
the USS module is already powered up, then the PSQ initiates a new measurement immediately.
UUPSCTL.USSPWRUPSEL determines the source of the USS_PWRREQ signal. When the PSQ detects
USS_PWRREQ signal, no additional event is accepted by the PSQ until the measurement is complete.
UUPSCTL.USS_BUSY indicates whether or not the USS module is in a power transition or performing a
measurement. While UUPSCTL.USS_BUSY = 1, the PSQ ignores the USS_PWRREQ signal (0
→
1).
Reset and Low Power Bias Mode control signals
On device Power Up the all USS submodules are kept in reset state. Set UUPSCTL.SWRST = 0 to
release reset and put the module into operation mode.
The operation mode has to be selected before the USS is powered up. For Auto mode and Register Mode
set SAPGMCNF.LPBE=0.
To select Low Power Bias Mode set SAPHMCNF.LPBE=1. SAPHMCNF.LPBE shall only be changed
while the PSQ is in OFF state.
•
USS_SWRST:
SW reset signal fo all USS submodules.
•
ASQ_LPBE:
Enables Low Power Bias operation mode here the ASQ takes has full control over the
input multiplexer and channel selection.
Power-up control signals
When USS_PWRREQ = 0
→
1 is detected, the PSQ starts the power-up sequence if the USS module has
not been powered up (UUPSCTL.UPSTATE = 0). The PSQ requests the required reference voltage and
currents, then enables the USS LDO and enables HSPLL. When the PLL is locked, generate the
PSQ_START signal to ASQ.
•
PSQ_SREFREQ:
Request signal to the share reference module.
•
PSQ_LDOUP:
Enables the USS LDO after the reference voltage and currents from BIAS_REF module
are settled.
•
PSQ_PLLUP:
Enables HSPLL when UUPSCTL.LDORDY = 1.
•
PSQ_START:
PSQ to ASQ to start a new measurement sequence. The PSQ asserts the signal when
IREF_MOD, USS LDO, and HSPLL are fully settled and UUPSCTL.ASQEN bit = 1.
•
PSQ_STOP:
PSQ to ASQ to stop the existing measurement immediately. The PSQ asserts the signal
when UUPSCTL.USSPWRDN = 1 or UUPSCTL.USSSTOP = 1.
Measurement control signals
When USS_START = 0
→
1 is detected, the ASQ starts a new measurement sequence based on the
timing information in the time mark registers (SAPHATM_A to SAPHATM_F).
•
ASQ_PPGTRG:
ASQ to PPG to generate excitation pules.