Ultra-Low Pwr UART 9600 Echo ISR, 32kHz ACLK

Nkolas Stavrou

Other Parts Discussed in Thread: MSP430F149

Dear friends,

Could anyone help with the following?

Iam trying to run at my MSP430F149 a program referred to Ultra-Low Pwr UART 9600 Echo ISR, 32kHz ACLK as presented at the exaples of slac014 zip.file.

Some of the remarks of this examples is:

1) USART RX ISR at high speed used with ultra low power technics.

2) Configure DCO that is used for USART baud rate generation

3) ISR must make sure that DCO clock remains enable for the UART to receive full character

4) TXign TEST

5) RXing test

Regarding the above, i started run program, but this stucked after sentence CALL #SET_DCO which corresponds to a subroutine which Sets DCO to selected frequency based on Delta.

More clearly stucked the time the:

Test_DCO bit.w #CCIFG,&CCTL2 ; Test capture flag
jz Test_DCO ;

when this try to test if capture interrupt occured showing that CAPTURE doesnt occured.

I have made all possible changes to run but nothing. If someone can help me pass this problem, i would greatfull.

Thanks,

regards Nick.

over 16 years ago

0 old_cow_yellow over 16 years ago

Guru 58965 points

Do you have a 32kHz crystal? If not, or if it is not oscillating, there is nothing to capture and the capture flag will never set.

0 Nkolas Stavrou over 16 years ago in reply to old_cow_yellow

Prodigy 240 points

Hello again,

Yes i have 32Khz watch crystal and i have made all neccessary actions. Please see below regarding 32KHz:

SetupBC bis.b #DIVA_3,&BCSCTL1 ; ACLK = LFXT1CLK/8

Also i have used as a referrence the: f_ref SET 32768 .

I just made a change on program regarding DCO_SET and seems at least that the interrupt capture is working. I enable the interrupt by my own including bis.w #CCIFG,&CCTL2 (SEE BELOW). Cature enabled, is making the test, it is set , after it's reset and start making the adjustements. The problem is that CCR2 has not any content, the comparison is being made and INCDCO proceedure starts, without in the end, DCO to be callibrated.

I would be gratefull if you could help me.

                          clr.w   R15                     ;
Setup_CC2   mov.w   #CM_1+CCIS_1,&CCTL2   ; CAP, ACLK
Setup_TA       mov.w   #TASSEL_2+MC_2+TACLR,&TACTL   ; SMCLK, ContMode, clr
Test_DCO    bis.w   #CCIFG,&CCTL2          ; Test capture flag
                       jz      Test_DCO                ;
                       bic.w   #CCIFG,&CCTL2           ; Clear capture flag

djDCO      mov.w   &CCR2,R14               ; R14 = captured SMCLK
                   sub.w   R15,R14                 ; R14 = capture difference
                 mov.w   &CCR2,R15               ; R15 = captured SMCLK
                cmp.w   #Delta,R14              ; Delta = SMCLK/(32768/8)
               jlo     IncDCO                  ;
                jeq     DoneDCO                 ;
DecDCO      dec.b   &DCOCTL                 ; Slow DCO with DCO and MOD
            jc      Test_DCO                ; Slower?
            cmp.b   #XT2OFF+DIVA_3,&BCSCTL1 ; Can RSEL.x be decremented?
            jz      DoneDCO                 ; jmp>DCO at slowest setting
            dec.b   &BCSCTL1                ; Decrement RSEL.x
            jmp     Test_DCO                ;
IncDCO      inc.b   &DCOCTL                 ; Speed DCO with DCO and MOD
            jnc     Test_DCO                ; Faster?
            cmp.b   #XT2OFF+DIVA_3+07h,&BCSCTL1 ; Can RSEL.x be increased?
            jz      DoneDCO                 ; jmp> DCO at fastest setting
            inc.b   &BCSCTL1                ; Increment RSEL.x
            jmp     Test_DCO                ;
DoneDCO     clr.w   &CCTL2                  ; Stop CCR2
            clr.w   &TACTL                  ; Stop timer_A
            ret                             ; Return from subroutine

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Ultra-Low Pwr UART 9600 Echo ISR, 32kHz ACLK