参数资料
型号: ST7PL35F2UA/XXXE
厂商: STMICROELECTRONICS
元件分类: 微控制器/微处理器
英文描述: 8-BIT, MROM, 8 MHz, MICROCONTROLLER, QCC20
封装: 5 X 6 MM, ROHS COMPLIANT, QFN-20
文件页数: 127/168页
文件大小: 2955K
代理商: ST7PL35F2UA/XXXE
Obsolete
Product(s)
- Obsolete
Product(s)
ST7L34, ST7L35, ST7L38, ST7L39
61/168
DUAL 12-BIT AUTORELOAD TIMER 3 (cont’d)
Long input capture
Pulses that last between 8s and 2s can be meas-
ured with an accuracy of 4s if fOSC = 8 MHz in the
following conditions:
– The 12-bit AT3 Timer is clocked by the Lite Timer
(RTC pulse: CK[1:0] = 01 in the ATCSR register)
– The ICS bit in the ATCSR2 register is set so that
the LTIC pin is used to trigger the AT3 Timer cap-
ture.
– The signal to be captured is connected to LTIC
pin
– Input Capture registers LTICR, ATICRH and
ATICRL are read
This configuration allows to cascade the Lite Timer
and the 12-bit AT3 Timer to get a 20-bit input cap-
ture value. Refer to Figure 44.
Figure 44. Long Range Input Capture Block Diagram
Notes:
1. Since the input capture flags (ICF) for both tim-
ers (AT3 Timer and LT Timer) are set when signal
transition occurs, software must mask one inter-
rupt by clearing the corresponding ICIE bit before
setting the ICS bit.
2. If the ICS bit changes (from 0 to 1 or from 1 to
0), a spurious transition might occur on the input
capture signal because of different values on LTIC
and ATIC. To avoid this situation, it is recommend-
ed to do as follows:
First, reset both ICIE bits.
Then set the ICS bit.
Reset both ICF bits.
And then set the ICIE bit of desired interrupt.
3. How to compute a pulse length with long input
capture feature.
As both timers are used, computing a pulse length
is not straight-forward. The procedure is as fol-
lows:
– At the first input capture on the rising edge of the
pulse, we assume that values in the registers are
as follows:
LTICR = LT1
ATICRH = ATH1
ATICRL = ATL1
Hence ATICR1 [11:0] = ATH1 & ATL1
Refer to Figure 45.
LTIC
ATIC
ICS
1
0
12-bit Input Capture Register
OFF
fCPU
fLTIMER
12-bit Upcounter1
12-bit AutoReload Register
8-bit Input Capture Register
8-bit Timebase Counter1
fOSC/32
LTICR
CNTR1
ATICR
ATR1
8 LSB bits
12 MSB bits
LITE TIMER
12-bit ARTIMER
20
cascaded
bits
1
相关PDF资料
PDF描述
ST7L35F2UA/XXXRE 8-BIT, MROM, 8 MHz, MICROCONTROLLER, QCC20
ST7L35F2UC/XXXRE 8-BIT, MROM, 8 MHz, MICROCONTROLLER, QCC20
ST7L39F2MC/XXXE 8-BIT, MROM, 8 MHz, MICROCONTROLLER, PDSO20
ST7L39F2UC/XXXRE 8-BIT, MROM, 8 MHz, MICROCONTROLLER, QCC20
ST7PL34F2MC/XXXE 8-BIT, MROM, 8 MHz, MICROCONTROLLER, PDSO20
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