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Frequently asked questions

LPC2000 Family Peripherals, Timers FAQ

Q What is the finest resolution on the LPC2104/5/6 PWM?
A The finest resolution is (1/processor clock). If the maximum clock is 60MHz, then the resolution is just over 16ns.
Q Does the PWM block use the same timer counters as the general purpose timers?
A No. The PWM has its own set of timer counter registers.
Q I am not using the RTC in my application. How should the RTC pins be configured?
A RTC crystal pins should be left floating, and Vbat should be tied to Vdd.
Q Once the watchdog is started, can it be disabled?
A No. Once the watchdog is enabled, it runs forever.
Q I see some issues while using the watchdog. I think the chip is issuing an internal reset during the feed sequence. Can this happen?
A
The WDFEED sequence may be corrupted because an interrupt is occurring in between the feed sequences of 0xAA and 0x55. Disable interrupts before the feed sequence and then re-enable them. In some LPC2000 devices, this behavior is not seen. Please check the user manual of the specific device for up-to-date information. Application note AN10414 further discusses this issue.
Q Does the LPC213x/4x Vbat keep the SRAM alive when the part is powered down?
A The Vbat on the LPC213x and LPC214x series is for the RTC only. It does not keep the RAM alive when power is removed.
Q Is battery RAM provided for any of the LPC2000 devices?
A LPC23xx and LPC24xx devices have 2KB of battery RAM provided which can hold all the vital information in deep power down mode.
Q Can the RTC handle sub-second interrupts?
A Yes, but only in the LPC23xx and LPC24xx series is this feature incorporated.

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