1. Lecture 10: TI MSP430 Timers and Capture Modes
ECE 447 Fall 2009
Lecture 10: TI MSP430
Timers and Capture Modes

2. Timer_A Overview Timer Block Capture/compare channels
The core, based on 16-bit register TAR
Can chose sources for clock and freq division
Timer block has no output
Flag TAIFG is raised when counter returns to 0
Capture/compare channels
Capture an input, record value in TAR triggered by TACCRn
Compare TAR with the value stored in TACCRn
Request an Interrupt by setting its flag TACCRn CCFIG
Sample an input at a compare event

3. ECE 447: MSP430 Timer_A System
Generating delays - imposing a specific delay
between two points in the program by polling.
label 1
instr1
instr2
delay
label2
instrN

4. ECE 447: MSP430 Timer_A System
2. Input capture - measuring the time between signal
edges
start
stop
start
stop
3. Output compare - generating signals with the given
timing characteristics
single pulse
periodical signal
pulse width
period

5. ECE 447: MSP430 Timer_A System
4. Real Time Clock– Produce a periodic signal for
the MSP430.
period
The Real Time Clock Interrupt implements a hardware based time of day clock that can be used by the software.

6. ECE447: MSP430 Timer I/O Pins and Channels - 4618

7. ECE447: MSP430 Compare/Capture Block Diagram.

8. MSP430xx4xx Implementation of Timer_A

9. Timer_A Interrupt Schematic

10. Timer_A MSP430xx4xx Registers

11. TACTL: Timer_A Control Register

12. TAR: Timer_A Register

13. TACCRx: Timer_A Capture/Compare Register

14. TACCTLx: Capture/Compare Control Register

15. TAIV: Timer_A Interrupt Vector Register

16. ECE447: MPS430 Timer_A input clocks and dividers

17. ECE447: Measuring Pulse Widths
100 s < width < Configured Period (previous table)
start
stop
width  100 s
start
stop
width  Configured Period (previous table)
start
stop
Timer overflows

18. ECE 447: Measuring intervals <216 clock cycles
FFFF
stop
start

19. ECE 447: Measuring intervals <216 clock cycles (overflow)
FFFF
start
stop

20. ECE 447: Measuring intervals >216 clock cycles
FFFF
stop R
start

21. ECE 447: Measuring intervals >216 clock cycles3
N=4
FFFF R1
start
R1+R2=R
stop R2