ST72C171 datasheet(73/152 Pages) STMICROELECTRONICS

73 / 152 page

ST72C171

73/152

PWM AUTO-RELOAD TIMER (Cont’d)

Input capture function

This mode allows the measurement of external

signal pulse widths through ICRx registers.

Each input capture can generate an interrupt inde-

pendently on a selected input signal transition.

This event is flagged by a set of the corresponding

CFx bits of the Input Capture Control/Status regis-

ter (ICCSR).

These

input

capture

interrupts

are

enabled

through the CIEx bits of the ICCSR register.

The active transition (falling or rising edge) is soft-

ware programmable through the CSx bits of the

ICCSR register.

The read only input capture registers (ICRx) are

used to latch the auto-reload counter value when a

transition is detected on the ARTICx pin (CFx bit

set in ICCSR register). After fetching the interrupt

vector, the CFx flags can be read to identify the in-

terrupt source.

Note: After a capture detection, data transfer in

the ICRx register is inhibited until it is read (clear-

ing the CFx bit).

The timer interrupt remains pending while the CFx

flag is set when the interrupt is enabled (CIEx bit

set). This means, the ICRx register has to be read

at each capture event to clear the CFx flag.

The timing resolution is given by auto-reload coun-

ter cycle time (1/fCOUNTER).

Note: During HALT mode, if both input capture

and external clock are enabled, the ICRx register

value is not guaranteed if the input capture pin and

the external clock change simultaneously.

External interrupt capability

This mode allows the Input capture capabilities to

be used as external interrupt sources. The inter-

rupts are generated on the edge of the ARTICx

signal.

The edge sensitivity of the external interrupts is

programmable (CSx bit of ICCSR register) and

they are independently enabled through CIEx bits

of the ICCSR register. After fetching the interrupt

vector, the CFx flags can be read to identify the in-

terrupt source.

During HALT mode, the external interrupts can be

used to wake up the micro (if the CIEx bit is set).

Figure 46. Input Capture Timing Diagram

04h

COUNTER

01h

fCOUNTER

xxh

02h

03h

05h

06h

07h

04h

ARTICx PIN

CFx FLAG

ICRx REGISTER

INTERRUPT

ST72C171 Fiches technique(PDF) 73 Page - STMicroelectronics

ST72C171 Fiches technique(HTML) 73 Page - STMicroelectronics

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 ...More

Fiches technique Télécharger

Lien URL