参数资料
型号: PIC16LF628T-04/SS
厂商: Microchip Technology
文件页数: 117/170页
文件大小: 0K
描述: IC MCU FLASH 2KX14 COMP 20SSOP
产品培训模块: Asynchronous Stimulus
标准包装: 1,600
系列: PIC® 16F
核心处理器: PIC
芯体尺寸: 8-位
速度: 4MHz
连通性: UART/USART
外围设备: 欠压检测/复位,POR,PWM,WDT
输入/输出数: 16
程序存储器容量: 3.5KB(2K x 14)
程序存储器类型: 闪存
EEPROM 大小: 128 x 8
RAM 容量: 224 x 8
电压 - 电源 (Vcc/Vdd): 2 V ~ 5.5 V
振荡器型: 内部
工作温度: 0°C ~ 70°C
封装/外壳: 20-SSOP(0.209",5.30mm 宽)
包装: 带卷 (TR)
PIC16F62X
DS40300C-page 48
Preliminary
2003 Microchip Technology Inc.
7.3
Timer1 Operation in
Asynchronous Counter Mode
If control bit T1SYNC (T1CON<2>) is set, the external
clock input is not synchronized. The timer continues to
increment asynchronous to the internal phase clocks.
The timer will continue to run during SLEEP and can
generate an interrupt on overflow which will wake-up
the processor. However, special precautions in soft-
ware are needed to read/write the timer (Section 7.3.2).
In Asynchronous Counter mode, Timer1 can not be
used
as
a
time-base
for
capture
or
compare
operations.
7.3.1
EXTERNAL CLOCK INPUT TIMING
WITH UNSYNCHRONIZED CLOCK
If control bit T1SYNC is set, the timer will increment
completely asynchronously. The input clock must meet
certain minimum high-time and low-time requirements.
Refer to the appropriate Electrical Specifications
section, Timing Parameters 45, 46, and 47.
7.3.2
READING AND WRITING TIMER1 IN
ASYNCHRONOUS COUNTER
MODE
Reading TMR1H or TMR1L while the timer is running,
from an external asynchronous clock, will ensure a
valid read (taken care of in hardware). However, the
user should keep in mind that reading the 16-bit timer
in two 8-bit values itself poses certain problems since
the timer may overflow between the reads.
For writes, it is recommended that the user simply stop
the timer and write the desired values. A write
contention may occur by writing to the timer registers
while the register is incrementing. This may produce an
unpredictable value in the timer register.
Reading
the
16-bit
value
requires
some
care.
Example 7-1 is an example routine to read the 16-bit
timer value. This is useful if the timer cannot be
stopped.
EXAMPLE 7-1:
READING A 16-BIT FREE-
RUNNING TIMER
; All interrupts are disabled
MOVF
TMR1H, W
;Read high byte
MOVWF
TMPH
;
MOVF
TMR1L, W
;Read low byte
MOVWF
TMPL
;
MOVF
TMR1H, W
;Read high byte
SUBWF
TMPH,
W
;Sub 1st read
; with 2nd read
BTFSC
STATUS,Z
;Is result = 0
GOTO
CONTINUE
;Good 16-bit read
;
; TMR1L may have rolled over between the read
; of the high and low bytes. Reading the high
; and low bytes now will read a good value.
;
MOVF
TMR1H, W
;Read high byte
MOVWF
TMPH
;
MOVF
TMR1L, W
;Read low byte
MOVWF
TMPL
;
; Re-enable the Interrupts (if required)
CONTINUE
;Continue with your code
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