mc68hc908gr16 Freescale Semiconductor, Inc, mc68hc908gr16 Datasheet - Page 232

• Manufacturer Part Number: mc68hc908gr16
• Description: M68hc08 Microcontrollers Microcontroller
• Manufacturer: Freescale Semiconductor, Inc

Timer Interface Module (TIM)
PS[2:0] — Prescaler Select Bits
18.9.2 TIM Counter Registers
The two read-only TIM counter registers contain the high and low bytes of the value in the TIM 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.
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.
232
These read/write bits select one of the seven prescaler outputs as the input to the TIM counter as
18-2
shows. Reset clears the PS[2:0] bits.
Address: T1CNTH, $0021 and T2CNTH, $002C
Address: T1CNTL, $0022 and T2CNTL, $002D
Setting the TSTOP and TRST bits simultaneously stops the TIM counter at
a value of $0000.
Reset:
Reset:
Read:
Read:
Write:
Write:
PS2
Bit 15
0
0
0
0
1
1
1
1
Bit 7
Bit 7
Bit 7
0
0
Figure 18-6. TIM Counter Registers High (TCNTH)
Figure 18-7. TIM Counter Registers Low (TCNTL)
= Unimplemented
= Unimplemented
14
PS1
6
0
6
6
0
0
0
1
1
0
0
1
1
MC68HC908GR16 Data Sheet, Rev. 5.0
Table 18-2. Prescaler Selection
13
5
0
5
5
0
PS0
0
1
0
1
0
1
0
1
NOTE
NOTE
12
4
0
4
4
0
Internal bus clock ÷ 1
Internal bus clock ÷ 2
Internal bus clock ÷ 4
Internal bus clock ÷ 8
Internal bus clock ÷ 16
Internal bus clock ÷ 32
Internal bus clock ÷ 64
Not available
11
3
0
3
3
0
TIM Clock Source
10
2
0
2
2
0
1
9
0
1
1
0
Freescale Semiconductor
Bit 0
Bit 8
Bit 0
Bit 0
0
0
Table