ST10F272Z2_08 datasheet(61/189 Pages) STMICROELECTRONICS

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ST10F272Z2

General purpose timer unit

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General purpose timer unit

The GPT unit is a flexible multifunctional timer/counter structure which is used for time

related tasks such as event timing and counting, pulse width and duty cycle measurements,

pulse generation, or pulse multiplication. The GPT unit contains five 16-bit timers organized

into two separate modules GPT1 and GPT2. Each timer in each module may operate

independently in several different modes, or may be concatenated with another timer of the

same module.

11.1

GPT1

Each of the three timers T2, T3, T4 of the GPT1 module can be configured individually for

one of four basic modes of operation: timer, gated timer, counter mode and incremental

interface mode.

In timer mode, the input clock for a timer is derived from the CPU clock, divided by a

programmable prescaler.

In counter mode, the timer is clocked in reference to external events.

Pulse width or duty cycle measurement is supported in gated timer mode where the

operation of a timer is controlled by the ‘gate’ level on an external input pin. For these

purposes, each timer has one associated port pin (TxIN) which serves as gate or clock

input.

Table 35 and Table 36 list the timer input frequencies, resolution and periods for each pre-

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

In Incremental Interface Mode, the GPT1 timers (T2, T3, T4) can be directly connected to

the incremental position sensor signals A and B by their respective inputs TxIN and TxEUD.

Direction and count signals are internally derived from these two input signals so that the

contents of the respective timer Tx corresponds to the sensor position. The third position

sensor signal TOP0 can be connected to an interrupt input.

Timer T3 has output toggle latches (TxOTL) which changes state on each timer over flow /

underflow. The state of this latch may be output on port pins (TxOUT) for time out monitoring

of external hardware components, or may be used internally to clock timers T2 and T4 for

high resolution of long duration measurements.

In addition to their basic operating modes, timers T2 and T4 may be configured as reload or

capture registers for timer T3.

Table 35.

GPT1 timer input frequencies, resolutions and periods at 40 MHz

fCPU = 40 MHz

Timer Input Selection T2I / T3I / T4I

000b

001b

010b

011b

100b

101b

110b

111b

Pre-scaler

factor

128

256

512

1024

Input frequency

5 MHz

2.5 MHz

1.25 MHz

625 kHz

312.5 kHz 156.25 kHz 78.125 kHz

39.1 kHz

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