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参数资料
| 型号： | ST72121J2T6/XXX |
| 厂商： | STMICROELECTRONICS |
| 元件分类： | 微控制器/微处理器 |
| 英文描述： | 8-BIT, MROM, 16 MHz, MICROCONTROLLER, PQFP44 |
| 封装： | PLASTIC, TQFP-44 |
| 文件页数： | 27/87页 |
| 文件大小： | 1365K |
| 代理商： | ST72121J2T6/XXX |
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ST72121
16-BIT TIMER (Cont’d)
16-bit read sequence: (from either the Counter
Register or the Alternate Counter Register).
The user must read the MSB first, then the LSB
value is buffered automatically.
This buffered value remains unchanged until the
16-bit read sequence is completed, even if the
user reads the MSB several times.
After a complete reading sequence, if only the
CLR register or ACLR register are read, they re-
turn the LSB of the count value at the time of the
read.
An overflow occurs when the counter rolls over
from FFFFh to 0000h then:
– The TOF bit of the SR register is set.
– A timer interrupt is generated if:
– TOIE bit of the CR1 register is set and
– I bit of the CC register is cleared.
If one of these conditions is false, the interrupt re-
mains pending to be issued as soon as they are
both true.
Clearing the overflow interrupt request is done in
two steps:
1. Reading the SR register while the TOF bit is set.
2. An access (read or write) to the CLR register.
Notes: The TOF bit is not cleared by accesses to
ACLR register. This feature allows simultaneous
use of the overflow function and reads of the free
running counter at random times (for example, to
measure elapsed time) without the risk of clearing
the TOF bit erroneously.
The timer is not affected by WAIT mode.
In HALT mode, the counter stops counting until the
mode is exited. Counting then resumes from the
previous count (MCU awakened by an interrupt) or
from the reset count (MCU awakened by a Reset).
4.3.3.2 External Clock
The external clock (where available) is selected if
CC0=1 and CC1=1 in CR2 register.
The status of the EXEDG bit determines the type
of level transition on the external clock pin EXT-
CLK that will trigger the free running counter.
The counter is synchronised with the falling edge
of the internal CPU clock.
At least four falling edges of the CPU clock must
occur between two consecutive active edges of
the external clock; thus the external clock frequen-
cy must be less than a quarter of the CPU clock
frequency.
LSB is buffered
Read MSB
At t0
Read LSB
Returns the buffered
LSB value at t0
At t0 +
t
Other
instructions
Beginning of the sequence
Sequence completed
33
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相关代理商/技术参数 |
参数描述 |
|---|---|
| ST72121J4 | 制造商:未知厂家 制造商全称:未知厂家 功能描述:8-BIT MICROCONTROLLER (MCU) WITH 8 TO 16 K ROM/OTP/EPROM. 384 TO 512 BYTES RAM. WDG. SCI. SPI & 2 TIMERS - SDIP42. TQFP44 |
| ST72124J | 制造商:STMICROELECTRONICS 制造商全称:STMicroelectronics 功能描述:8-BIT MCU WITH SINGLE VOLTAGE FLASH MEMORY, ADC, 16-BIT TIMERS, SPI, SCI INTERFACES |
| ST72124J2 | 制造商:STMICROELECTRONICS 制造商全称:STMicroelectronics 功能描述:8-BIT MCU WITH SINGLE VOLTAGE FLASH MEMORY, ADC, 16-BIT TIMERS, SPI, SCI INTERFACES |
| ST72124J2B | 制造商:STMICROELECTRONICS 制造商全称:STMicroelectronics 功能描述:8-BIT MCU WITH SINGLE VOLTAGE FLASH MEMORY, ADC, 16-BIT TIMERS, SPI, SCI INTERFACES |
| ST72124J2B1 | 制造商:STMICROELECTRONICS 制造商全称:STMicroelectronics 功能描述:8-BIT MCU WITH SINGLE VOLTAGE FLASH MEMORY, ADC, 16-BIT TIMERS, SPI, SCI INTERFACES |
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