Datasheet

Registers
MC68HC908QB8 Data Sheet, Rev. 3
Freescale Semiconductor 185
16.8.2 TIM Counter Registers
The two read-only TIM counter registers contain the high and low bytes of the value in the counter.
Reading the high byte (TCNTH) latches the contents of the low byte (TCNTL) into a buffer. Subsequent
reads of TCNTH do not affect the latched TCNTL value until TCNTL is read. Reset clears the TIM counter
registers. Setting the TIM reset bit (TRST) also clears the TIM counter registers.
NOTE
If you read TCNTH during a break interrupt, be sure to unlatch TCNTL by
reading TCNTL before exiting the break interrupt. Otherwise, TCNTL
retains the value latched during the break.
16.8.3 TIM Counter Modulo Registers
The read/write TIM modulo registers contain the modulo value for the counter. When the counter reaches
the modulo value, the overflow flag (TOF) becomes set, and the counter resumes counting from $0000
at the next timer clock. Writing to the high byte (TMODH) inhibits the TOF bit and overflow interrupts until
the low byte (TMODL) is written. Reset sets the TIM counter modulo registers.
NOTE
Reset the counter before writing to the TIM counter modulo registers.
Bit 7654321Bit 0
Read: Bit 15 Bit 14 Bit 13 Bit 12 Bit 11 Bit 10 Bit 9 Bit 8
Write:
Reset:00000000
= Unimplemented
Figure 16-5. TIM Counter High Register (TCNTH)
Bit 7654321Bit 0
Read: Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
Write:
Reset:00000000
= Unimplemented
Figure 16-6. TIM Counter Low Register (TCNTL)
Bit 7654321Bit 0
Read:
Bit15 Bit14 Bit13 Bit12 Bit11 Bit10 Bit9 Bit8
Write:
Reset:11111111
Figure 16-7. TIM Counter Modulo High Register (TMODH)
Bit 7654321Bit 0
Read:
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0
Write:
Reset:11111111
Figure 16-8. TIM Counter Modulo Low Register (TMODL)