Texas Instruments MSP430x1xx - Manual (Page 181)

Timer_B Operation
11-5
Timer_B
11.2 Timer_B Operation
The 16-bit timer has four modes of operation selectable with the MC0 and MC1
bits in the TBCTL register and four selectable lengths, also configured in the
TBCTL register. The timer increments or decrements (depending on mode of
operation) with each rising edge of the clock signal. The timer can be read or
written to with software. Additionally, the timer can generate an interrupt with
its ripple-carry output when it overflows.
11.2.1 Timer Length
Timer_B is configurable to operate as a true 8-bit, 10-bit, 12-bit, or 16-bit timer.
The length of the counter is configured in the TBCTL register. Leading bits are
read as zero in 8-bit, 10-bit, and 12-bit mode. Data written to the TBR register
in 8-bit, 10-bit, and 12-bit mode will show leading 0s. The maximum count
value, TBR
(max)
, for the various lengths is:
Timer B Config ration TBR Timer_B Configuration TBR
(max)
16-bit 0FFFFh
12-bit 0FFFh
10-bit 03FFh
8-bit 0FFh
11.2.2 Timer Mode Control
The timer has four modes of operation as shown in Figure 11–2 and described
in Table 11–1: stop, up, continuous, and up/down. The operating mode is soft-
ware selectable with the MC0 and MC1 bits in the TBCTL register.
Figure 11–2. Mode Control
CLK
16-Bit Timer †
RC
15 0
Data
POR
Mode
Control
MC1 MC0
Equ0
Carry/Zero Set_TBIFG
0
0
1
1 0
1
0
1 Stop Mode
Up Mode
Continuous Mode
Up/Down Mode
Timer Clock
† Length is selectable for 8-, 10-, 12-, or 16-bit operation.