Revision(s) Affected

0, A, B

Details

The ADC can get into a non-responsive state when the ADCCTL2[ADCNONOVERLAP] is modified while a conversion is in progress. When in this condition, no further conversion from the ADC will be possible without a device reset.

There are two different ways to cause this condition:

• Writing to ADCCTL2[ADCNONOVERLAP] while a conversion is in progress.
• Writing to ADCCTL1[RESET] while a conversion is in progress.

Workaround(s)

Follow this sequence to modify ADCCTL2[ADCNONOVERLAP] or write ADCCTL1[RESET]:

1. Set all SOC trigger sources ADCSOCxCTL[TRIGSEL] to 0.
2. Set all ADCINTSOCSEL1/2 to 0.
3. Ensure there is not another SOC pending (This can be accomplished by polling SOC Flags).
4. Wait for all conversions to complete.
   1. ADCCTL2[CLKDIV2EN] = 0, ADCCTL2[CLKDIV4EN] = x → (ACQPS + 13 ) * 1 SYSCLKs
   2. ADCCTL2[CLKDIV2EN] = 1, ADCCTL2[CLKDIV4EN] = 0 → (ACQPS + 13 ) * 2 SYSCLKs
   3. ADCCTL2[CLKDIV2EN] = 1, ADCCTL2[CLKDIV4EN] = 1 → (ACQPS + 13 ) * 4 SYSCLKs
5. Modify ADCCTL2[ADCNONOVERLAP] or write ADCCTL1[RESET].

An example code follows.

EALLOW;
// Set all SOC trigger sources to software
AdcRegs.ADCSOC0CTL.bit. TRIGSEL  = 0;
AdcRegs.ADCSOC1CTL.bit. TRIGSEL  = 0;
AdcRegs.ADCSOC2CTL.bit. TRIGSEL  = 0;
AdcRegs.ADCSOC3CTL.bit. TRIGSEL  = 0;
AdcRegs.ADCSOC4CTL.bit. TRIGSEL  = 0;
AdcRegs.ADCSOC5CTL.bit. TRIGSEL  = 0;
AdcRegs.ADCSOC6CTL.bit. TRIGSEL  = 0;
AdcRegs.ADCSOC7CTL.bit. TRIGSEL  = 0;
AdcRegs.ADCSOC8CTL.bit. TRIGSEL  = 0;
AdcRegs.ADCSOC9CTL.bit. TRIGSEL  = 0;
AdcRegs.ADCSOC10CTL.bit. TRIGSEL  = 0;
AdcRegs.ADCSOC11CTL.bit. TRIGSEL  = 0;
AdcRegs.ADCSOC12CTL.bit. TRIGSEL  = 0;
AdcRegs.ADCSOC13CTL.bit. TRIGSEL  = 0;
AdcRegs.ADCSOC14CTL.bit. TRIGSEL  = 0;
AdcRegs.ADCSOC15CTL.bit. TRIGSEL  = 0;
// Set all ADCINTSOCSEL1/2 to 0.
    AdcRegs.ADCINTSOCSEL1.bit.SOC0  = 0;
    AdcRegs.ADCINTSOCSEL1.bit.SOC1  = 0;
    AdcRegs.ADCINTSOCSEL1.bit.SOC2  = 0;
    AdcRegs.ADCINTSOCSEL1.bit.SOC3  = 0;
    AdcRegs.ADCINTSOCSEL1.bit.SOC4  = 0;
    AdcRegs.ADCINTSOCSEL1.bit.SOC5  = 0;
    AdcRegs.ADCINTSOCSEL1.bit.SOC6  = 0;
    AdcRegs.ADCINTSOCSEL1.bit.SOC7  = 0;
    AdcRegs.ADCINTSOCSEL2.bit.SOC8  = 0;
    AdcRegs.ADCINTSOCSEL2.bit.SOC9  = 0;
    AdcRegs.ADCINTSOCSEL2.bit.SOC10 = 0;
    AdcRegs.ADCINTSOCSEL2.bit.SOC11 = 0;
    AdcRegs.ADCINTSOCSEL2.bit.SOC12 = 0;
    AdcRegs.ADCINTSOCSEL2.bit.SOC13 = 0;
    AdcRegs.ADCINTSOCSEL2.bit.SOC14 = 0;
    AdcRegs.ADCINTSOCSEL2.bit.SOC15 = 0;
// Ensure there is not another SOC pending
while (AdcRegs.ADCSOCFLG1.all != 0x0);
// Wait for conversions to complete
// Delay time based on ACQPS = 6 , ADCCTL2[CLKDIV2EN] = 1, ADCCTL2[CLKDIV4EN] = 0
// 7 + 13 ADC Clocks = 20 ADCCLKS -> 40 SYSCLKS
asm(" RPT#40||NOP");
// ADCCTL2[ADCNONOVERLAP] = <new value>;
// ADCCTL1[RESET] = 1;
EDIS;