Using UTMR as Signal Measurement Timer (SMT)

SMT is a 24-bit counter with advanced clock and gating logic, which can be configured for measuring a variety of digital signal parameters, such as pulse width, frequency and duty cycle, and the time difference between edges on two signals. A key feature that differentiates SMT from UTMR is the presence of two input signals (SMT signal and window) and two capture registers (SMTxCPW and SMTxCPR). UTMR has only one input signal (ERS) and one capture register. Thus, the UTMR might need to be reconfigured multiple times to measure different attributes in the same application. The following table shows UTMR settings in different SMT modes:

Table 1. UTMR Settings for Different SMT Modes

SMT MODE[3:0]

 SMT Mode UTMR Settings Comments
START RESET STOP Other
0000 Timer None (ON = 1) At PR Match None — —
0001 Gated Timer Rising ERS Edge At PR Match Either ERS Edge — Use SMT signal as ERS input.
0010 Period and Duty Cycle Measurement Rising ERS Edge At Start + PR Match

None (measures pulse-width)

Rising ERS Edge (measures period)

 — Use SMT signal as ERS input. TUxyCR capture register will capture either pulse-width or period based on the Stop condition, but not both simultaneously.
0011 High and low time Measurement Either ERS Edge At Start + PR Match Either ERS Edge — Use SMT signal as ERS input. TUxyCR capture register will capture high time, then low time, then high time, and so on. TUxyCR must be read before it is overwritten with new data.
Rising ERS Edge At Start + PR Match Either ERS Edge

EPOL = True level for high time

EPOL = Inverted level for low time

 Use SMT signal as ERS input. TUxyCR capture register will capture either high time or low time based on EPOL bit setting.
0100 Windowed Measurement Rising ERS Edge At Start + PR Match Rising ERS Edge — Use SMT window as ERS input.TUxyCR capture register will capture period of the window signal.
0101 Gated Windowed Measurement Rising ERS Edge At PR Match Either ERS Edge — Use SMT signal as ERS input. Use software to poll SMT window signal and reset counter manually using CLR command at every rising edge. Alternatively, interrupt-on-change can be used to monitor SMT window signal in software.
0110 Time of Flight Measurement Rising ERS Edge At Start + PR Match Either ERS Edge — Use CLC to send an XOR of SMT window and SMT signal via ERS. TUxyCR capture register captures the time of flight measurement.
0111 Capture None At PR Match Either ERS Edge — Use SMT signal as ERS input. TUxyCR capture register will first capture rising edge of ERS, then the falling edge of ERS, then the rising edge, and so on. TUxyCR must be read before it is overwritten with new data. PRAIF and PWAIF are both captured via CIF.
1000 Counter None (ON = 1) At PR Match None

CSYNC = Async for using external clock source

EPOL = Inverted for capturing at rising edge of ERS

 Use SMT signal as UTMR clock input. Use SMT window as ERS input. TUxyCR capture register will capture counter value at falling edge of ERS (or rising edge when EPOL = Inverted).
1001 Gated Counter Rising ERS Edge At PR Match Either ERS Edge CSYNC = Async for using external clock source Use SMT signal as UTMR clock input. Use SMT window as ERS input. TUxyCR capture register will capture counter value at falling edge of ERS. PWAIF is equivalent to CIF.
1010 Windowed Counter Rising ERS Edge At Start + PR Match

None (measures pulse-width)

Rising ERS Edge (measures period)

 CSYNC = Async for using external clock source Use SMT signal as UTMR clock input. Use SMT window as ERS input. TUxyCR capture register will capture either pulse-width or period based on the Stop condition, but not both simultaneously.