Operation of the USS Module
456
SLAU367P – October 2012 – Revised April 2020
Copyright © 2012–2020, Texas Instruments Incorporated
Ultrasonic Sensing Solution (USS, USS_A)
•
ASQ_ACQARM:
ASQ to SDHS to power up the SDHS module.
•
ASQ_ACQTRG:
ASQ to SDHS to start data conversion and transfer output data to target memory.
•
SHDS_ACQDONE:
SDHS to ASQ to acknowledge that the preconfigured sample size has been
captured.
Power-down control states and signals
When the desired measurement sequences finish execution, the power-down process starts. There are
three power states that can be chosen:
•
READY
: The USS module is fully powered up (no changes in power state).
•
STANDBY
: The USS module is powered off, but required reference voltage is kept on for faster
wakeup.
•
OFF
: The USS module is fully powered off.
The ASQ asserts ASQ_ACQDONE to acknowledge the PSQ that the measurement is compete.
Depending on the selected power state, ASQ_PDREQ or ASQ_STBYREQ can be asserted along with the
ASQ_ACQDONE signal.
•
ASQ_PDREQ:
Goes to OFF state.
•
ASQ_STDBYREQ:
Goes to STANDBY state.
•
ASQ_ASQDONE:
Indicates that the measurement is complete. If neither ASQ_PDREQ nor
ASQ_STDBYREQ is asserted, then stay in READY state.
Emergency measurement stop control signals
While the USS module is active, the current measurement sequence can be stopped at any time:
•
PSQ_STOP:
PSQ to ASQ to stop the current measurement immediately (when UUPSCTL.USSSTOP
= 1 or UUPSCTL.USSPWRDN = 1).
•
ASQ_PPGSTOP:
ASQ to PPG to stop pulse generation if the PPG is active.
•
ASQ_SDHSSTOP:
ASQ to SDHS to stop the data conversion and turn off the SDHS if the SDHS is
active.
Table 18-4. Control Signals Among USS Submodules
Source
Signal
Receiver
Function
Condition to Generate the Signal
UUPSCTL.SWR
ST
USS_SWRST
ASQ, PPG,
SAPH,
SDHS
Software reset to all USS
submodules
UUPSCTL.SWRST = 1
SAPHMCNF.LP
BE
ASQ_LPBE
PSQ
Indication to enter low-power bias
mode
SAPHMCNF.LPBE = 1
UUPSCTL.USS
PWRUP
USS_PWRREQ
PSQ
1.
Power up the USS module
2.
Assert PSQ_START if
UUPSCTL.ASQEN = 1
3.
If UUPSCTL.USS_BUSY = 1 or
UUPSCTL.UPSTATE = 2, the
signal is ignored
UUPSCTL.USSPWRUP = 0
→
1
Internal signal
See device-specific data sheet
Internal signal
See device-specific data sheet
Internal signal
See device-specific data sheet
PSQ
PSQ_SREFREQ
SREF
Shared reference request
USS_PWRREQ: 0
→
1 (valid)
PSQ_LDOUP
USS LDO
Enable USS LDO
SREF is ready
PSQ_PLLUP
HSPLL
Enable HSPLL
UUPSCTL.LDORDY = 1
PSQ_START
ASQ
Start a new measurement
UUPSCTL.UPSTATE = 3
PSQ_STOP
Stop the current measurement
immediately
UUPSCTL.USSPWRDN = 1,
UUPSCTL.USSSTOP = 1 or Enter
debug mode