MC68HC705C Motorola, MC68HC705C Datasheet - Page 96

• Manufacturer Part Number: MC68HC705C
• Description: HCMOS Microcontroller Unit
• Manufacturer: Motorola

Capture/Compare Timer
8.4.4 Alternate Timer Registers
Technical Data
96
NOTE:
Reading TRH returns the current value of the high byte of the counter
and causes the low byte to be latched into a buffer, as shown in
Figure
more than once. Reading TRL reads the transparent low byte buffer and
completes the read sequence of the timer registers.
To prevent interrupts from occurring between readings of TRH and TRL,
set the interrupt mask (I bit) in the condition code register before reading
TRH, and clear the mask after reading TRL.
The alternate timer registers (ATRH and ATRL) shown in
contain the current high and low bytes of the 16-bit counter. Reading
ATRH before reading ATRL causes ATRL to be latched until ATRL is
read. Reading does not affect the timer overflow flag (TOF). Writing to
the alternate timer registers has no effect.
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8-8. The buffer value remains fixed even if the high byte is read
15
Capture/Compare Timer
TIMER REGISTER HIGH
Figure 8-8. Timer Register Reads
READ TRH
INTERNAL DATA BUS
LATCH
8
7
7
TIMER REGISTER LOW
LOW BYTE BUFFER
MC68HC705C8A — Rev. 2.0
Figure 8-9
MOTOROLA
0
0
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