mc68hc05pv8 Freescale Semiconductor, Inc, mc68hc05pv8 Datasheet - Page 135

• Manufacturer Part Number: mc68hc05pv8
• Description: Hcmos Microcontroller Unit
• Manufacturer: Freescale Semiconductor, Inc

MC68HC(8)05PV8/A — Rev. 1.9
SI1 – Sample Input 1
SI2 – Sample Input 2
Accessing the timer status registers satisfies the first condition required
to clear status bits. The remaining step is to access the registers
corresponding to the status bit.
A problem can occur when using the timer overflow function and reading
the free-running counter at random times to measure an elapsed time.
Without incorporating the proper precautions into software, the timer
overflow flag could unintentionally be cleared if:
The counter alternate register contains the same value as the
free-running counter; therefore this alternate register can be read at any
time without affecting the timer overflow flag in the timer status register.
1. The timer status register is read or written when TOF is set, and
2. The LSB of the free-running counter is read but not for the purpose
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1 = Bit set when input capture 1 input is sampled high while output
0 = Bit cleared when input capture 1 input is sampled low while
1 = Bit set when input capture 2 input is sampled high while output
0 = Bit cleared when input capture 2 input is sampled low while
of servicing the flag
compare register 1 matches the free running counter
output compare register 1 matches the free running counter
compare register 2 matches the free running counter
output compare register 2 matches the free running counter
16-Bit Programmable Timer
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16-Bit Programmable Timer
Technical Data
Registers