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Chapter 40 Pulse Frequency Modulator
4.PFM Operation and Setting
4. PFM Operation and Setting
This section describes the following operations of the 16-bit pulse frequency mod (combining the
functionality of both reload counters).
1. The underflow output of reload counter channel 0 is connected internally to the trigger input reload
counter channel 1. The underflow output of reload counter channel 1 is connected internally to the
trigger input of reload counter channel 0.
2. Both counters must be set up with RELD = “0”. Counter 0 should then be started by software
trigger TRG = “1”. By starting counter 0 a high level is generated at the output. At the underflow
condition of counter 0, counter 1 is automatically reloaded and started by the internal trigger (falling
edge, set MOD1 = “1” for both counters) and a low level is generated at the output. At the underflow
condition of counter 1, counter 0 is automatically reloaded and started by the internal trigger and a high
level is generated at the output.
3. Interrupts can be set up on underflow condition of counter 0, counter 1 or both. The interrupts of
counter 0 and counter 1 are OR’ed together,
4. The default output is low level if both CNTE = “0”, and both INV = “0”.
