SDHS Functional Operation
585
SLAU367P – October 2012 – Revised April 2020
Copyright © 2012–2020, Texas Instruments Incorporated
Sigma-Delta High Speed (SDHS)
After the SDHS is triggered for power up, SDHSCTL5.SDHS_LOCK is automatically set to 1. When
SDHSCTL5.SDHS_LOCK = 1, the SDHSCTL3 register is locked. Both SDHSCTL3.TRIGEN and
SDHS_LOCK protect the SDHS registers from inadvertent modifications while the SDHS is active. The
PGA gain registers (SDHSCTL6) are not locked even after SDHS is powered up; however, take care
when updating the PGA gain while SDHS is performing data conversion. Expect a transition period before
the new gain is applied (see the device-specific data sheet for the PGA gain settling time).
Table 22-5. SDHSCTL3.TRIGEN Bit and SDHSCTL5.SDHS_LOCK Bit
Control Bit
Type
How to Set the Control Bit
Registers Locked
SDHSCTL3.TRIGEN
Read/Write
Write 1 to SDHSCTL3.TRIGEN bit
SDHSCTL0, SDHSCTL1, SDHSCTL2,
SDHSCTL7, SDHSWINHITH,
SDHSWINLOTH, and SDHSDTCDA
SDHSCTL5.SDHS_LOCK
Read Only
When SDHS_PWR_UP is asserted
SDHSCTL3
Table 22-6. Timing of the SDHS_LOCK bit
Type
SDHSCTL0.TRGSRC = 0
SDHSCTL0.TRGSRC = 1
SDHS power trigger
SDHSCTL4.SDHSON = 1 (by
software)
ASQ_ACQARM = 1 (from ASQ)
Time to set SDHS_LOCK bit
after the trigger
No delay
Delay = 4 × system clock 4 × (PLL clock period × 10)