ST10F271B datasheet(62/180 Pages) STMICROELECTRONICS

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General purpose timer unit

ST10F271B/ST10F271E

62/180

11.2

GPT2

The GPT2 module provides precise event control and time measurement. It includes two

timers (T5, T6) and a capture/reload register (CAPREL). Both timers can be clocked with an

input clock which is derived from the CPU clock via a programmable prescaler or with

external signals. The count direction (up/down) for each timer is programmable by software

or may additionally be altered dynamically by an external signal on a port pin (TxEUD).

Concatenation of the timers is supported via the output toggle latch (T6OTL) of timer T6

which changes its state on each timer overflow/underflow.

The state of this latch may be used to clock timer T5, or it may be output on a port pin

(T6OUT). The overflow / underflow of timer T6 can additionally be used to clock the

CAPCOM timers T0 or T1, and to cause a reload from the CAPREL register. The CAPREL

corresponding port pin (CAPIN), and timer T5 may optionally be cleared after the capture

procedure. This allows absolute time differences to be measured or pulse multiplication to

be performed without software overhead.

The capture trigger (timer T5 to CAPREL) may also be generated upon transitions of GPT1

timer T3 inputs T3IN and/or T3EUD. This is advantageous when T3 operates in Incremental

Interface Mode.

Table 36 and Table 37 list the timer input frequencies, resolution and periods for each pre-

scaler option at 40MHz and 64MHz CPU clock respectively.

Table 36.

GPT2 timer input frequencies, resolutions and periods at 40 MHz

CPU = 40MHz

Timer Input Selection T5I / T6I

000b

001b

010b

011b

100b

101b

110b

111b

Pre-scaler

factor

128

256

512

Input Freq

10MHz

5MHz

2.5MHz

1.25

MHz

625 kHz

312.5

kHz

156.25

kHz

78.125

kHz

Resolution

100ns

200ns

400ns

0.8µs

1.6µs

3.2µs

6.4µs

12.8µs

Period

maximum

6.55ms

13.1ms

26.2ms

52.4ms

104.8ms 209.7ms

419.4ms

838.9ms

Table 37.

GPT2 timer input frequencies, resolutions and periods at 64 MHz

CPU = 64MHz

Timer Input Selection T5I / T6I

000b

001b

010b

011b

100b

101b

110b

111b

Pre-scaler

factor

128

256

512

Input Freq

16MHz

8MHz

4MHz

2MHz

1 kHz

500 kHz

250 kHz

128 kHz

Resolution

62.5ns

125ns

250ns

0.5µs

1.0µs

2.0µs

4.0µs

8.0µs

Period

maximum

4.1ms

8.2ms

16.4ms

32.8ms

65.5ms

131.1ms

262.1ms

524.3ms

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