MC68HC908EY16 Datasheet, PDF (219/278 Pages) Motorola, Inc – Microcontrollers

I/O Registers
18.8.2 TIMB Counter Registers
The two read-only TIMB counter registers contain the high and low bytes of the value in the TIMB counter.
Reading the high byte (TBCNTH) latches the contents of the low byte (TBCNTL) into a buffer. Subsequent
reads of TBCNTH do not affect the latched TBCNTL value until TBCNTL is read. Reset clears the TIMB
counter registers. Setting the TIMB reset bit (TRST) also clears the TIMB counter registers.
NOTE
If TBCNTH is read during a break interrupt, be sure to unlatch TBCNTL by
reading TBCNTL before exiting the break interrupt. Otherwise, TBCNTL
retains the value latched during the break.
Register Name and Address
TBCNTH — $002C
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
TBCNTL — $002D
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 18-5. TIMB Counter Registers (TBCNTH and TBCNTL)
18.8.3 TIMB Counter Modulo Registers
The read/write TIMB modulo registers contain the modulo value for the TIMB counter. When the TIMB
counter reaches the modulo value, the overflow flag (TOF) becomes set, and the TIMB 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 TIMB counter modulo registers.
Register Name and Address
TBMODH — $002E
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
TBMODL — $002F
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 18-6. TIMB Counter Modulo Registers (TMODH and TMODL)
NOTE
Reset the TIMB counter before writing to the TIMB counter modulo registers.
MC68HC908EY16 • MC68HC908EY8 Data Sheet, Rev. 10
Freescale Semiconductor
219