MC68HC908EY16 Datasheet, PDF (203/278 Pages) Motorola, Inc – Microcontrollers

I/O Registers
17.8.2 TIMA Counter Registers
The two read-only TIMA counter registers contain the high and low bytes of the value in the TIMA counter.
Reading the high byte (TACNTH) latches the contents of the low byte (TACNTL) into a buffer. Subsequent
reads of TACNTH do not affect the latched TACNTL value until TACNTL is read. Reset clears the TIMA
counter registers. Setting the TIMA reset bit (TRST) also clears the TIMA counter registers.
NOTE
If TACNTH is read during a break interrupt, be sure to unlatch TACNTL by
reading TACNTL before exiting the break interrupt. Otherwise, TACNTL
retains the value latched during the break.
Register Name and Address
TACNTH — $0021
Bit 7
6
5
4
3
2
1
Bit 0
Read: BIT 15 BIT 14 BIT 13 BIT 12 BIT 11 BIT 10
BIT 9
BIT 8
Write: R
R
R
R
R
R
R
R
Reset: 0
0
0
0
0
0
0
0
Register Name and Address
TACNTL — $0022
Bit 7
6
5
4
3
2
1
Bit 0
Read: BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
Write: R
R
R
R
R
R
R
R
Reset: 0
0
0
0
0
0
0
0
R
= Reserved
Figure 17-5. TIMA Counter Registers (TACNTH and TACNTL)
17.8.3 TIMA Counter Modulo Registers
The read/write TIMA modulo registers contain the modulo value for the TIMA counter. When the TIMA
counter reaches the modulo value, the overflow flag (TOF) becomes set, and the TIMA 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 TIMA counter modulo registers.
Register Name and Address
TAMODH — $0023
Bit 7
6
5
4
3
2
1
Bit 0
Read:
BIT 15 BIT 14 BIT 13 BIT 12 BIT 11 BIT 10
BIT 9
BIT 8
Write:
Reset: 1
1
1
1
1
1
1
1
Register Name and Address
TAMODL — $0024
Bit 7
6
5
4
3
2
1
Bit 0
Read:
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
Write:
Reset: 1
1
1
1
1
1
1
1
Figure 17-6. TIMA Counter Modulo Registers (TMODH and TMODL)
NOTE
Reset the TIMA counter before writing to the TIMA counter modulo registers.
MC68HC908EY16 • MC68HC908EY8 Data Sheet, Rev. 10
Freescale Semiconductor
203