Hi there,
I would like to make sure that this code is enabling the external 32.768kHz watch crystal and also I would like to know how to enable the internal 6pF load capacitors for the crystal. I'm a hardware engineer so I will pass on the info to my software engineer. Thanks!
Andy.
void main(void){ BCSCTL1 |= XCAP_1; // ACLK/2 WDTCTL = WDT_ADLY_16; //250 // WDT 1s/4 interval timer IE1 |= WDTIE; // Enable WDT interrupt P1DIR = 0xF8; // All P1.x outputs P1OUT = 0; // All P1.x reset P2DIR = 0xFF; // All P2.x outputs P2OUT = 0; // All P2.x reset P1OUT |= 0x08; // initilize variables #if MY_DEBUG i_error = 0; led_on_mask = 0x08; mode = TEST_MODE; #else i_error = 0; led_on_mask = 0; mode = 0; #endif cnt_watering_hour = 0; cnt_watering = 0; upper_limit_hour[0] = 4; upper_limit_hour[1] = 6; upper_limit_hour[2] = 12; while(1)
The BOR/POR automatically enables the internal 6pF load capacitors for the crystal.
The line: " BCSCTL1 |= XCAP_1; // ACLK/2" does not make any sense.to me
The line: " P2DIR = 0xFF; // All P2.x outputs" seems incorrect too, I think BIT6 should be 0
Hi,
To add to OCY's post, see page 301 of the 2xx User's Guide, which gives bit settings for all internal cap values.
Regards,Brandon
DCAT - MSP430 ApplicationsTexas Instruments
Hi Brandon,
I can't find the information in the datasheet where it says what the default value for the BCSCTL3 (load capacitance) register is. The crystal I'm using has a specified load capacitance of 12.5pF in the datasheet. Can you please point me to this information so that I can verify I have the correct load capacitance selected?
The problem i'm seeing is that the processor doesn't always start up when i power on the board. I've narrowed it down to either the Vcc ramp rate affecting the reset behaviour or the crystal not starting. The supply comes up in about 50-100us. The startup seems to become more reliable the slower I make the supply ramp up.
Any advice much appreciated.
Andy: I can't find the information in the datasheet where it says what the default value for the BCSCTL3 (load capacitance) register is. The crystal I'm using has a specified load capacitance of 12.5pF in the datasheet. Can you please point me to this information so that I can verify I have the correct load capacitance selected?
Section 5.3 of the MSP430x2xx Family User's Guide (SLAU144) has the reset value of the BCSCTL3 in Table 5-1. This value is 0x05. Furthermore, the register definition for BCSCTL3 has the reset value of each bit field under the illustration. A XCAPx=01b equates to 6pF.
Brandon
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