L9803 datasheet(48/126 Pages) STMICROELECTRONICS

48 / 126 page

On-Chip Peripherals

L9803

48/126

These registers are readable and writable and are not affected by the timer hardware. A

reset event changes the OCiR value to 8000h.

Timing resolution is one count of the free running counter: (fCPU/CC[1:0]).

Procedure

To use the output compare function, select the following in the CR2 register:

–

Set the OCiE bit if an output is needed then the OCMPi pin is dedicated to the

output compare i function.

–

Select the timer clock (CC[1:0]) (see Table 9: Clock Control Bits).

And select the following in the CR1 register:

–

Select the OLVLi bit to applied to the OCMPi pins after the match occurs.

–

Set the OCIE bit to generate an interrupt if it is needed.

When a match is found between OCRi register and CR register:

–OCFi bit is set.

–The OCMPi pin takes OLVLi bit value (OCMPi pin latch is forced low during reset).

–

A timer interrupt is generated if the OCIE bit is set in the CR1 register and the I bit

is cleared in the CC register (CC).

The OCRi register value required for a specific timing application can be calculated using

the following formula:

Where:

∆t

= Output compare period (in seconds)

fCPU

= CPU clock frequency (in Hz)

PRESC

= Timer prescaler factor (2, 4 or 8 depending on CC[1:0] bits,

see Table 9: Clock Control Bits)

If the timer clock is an external clock, the formula

is:

∆OCiR = ∆t · f

EXT

Where:

∆t

= Output compare period (in seconds)

EXT

= External timer clock frequency (in hertz)

Clearing the output compare interrupt request (i.e.clearing the OCFi bit) is done by:

Reading the SR register while the OCFi bit is set.

An access (read or write) to the OCiLR register.

MS Byte

LS Byte

OCiROCiHR

OCiLR

∆OCiR

∆tf

CPU

⋅

PRESC

-----------------------

L9803 数据表(PDF) 48 Page - STMicroelectronics

L9803 数据表(HTML) 48 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

数据表下载