PIC16F8X
1998 Microchip Technology Inc.
DS30430C-page 27
6.0
TIMER0 MODULE AND TMR0
REGISTER
The Timer0 module timer/counter has the following
features:
8-bit timer/counter
Readable and writable
8-bit software programmable prescaler
Internal or external clock select
Interrupt on overflow from FFh to 00h
Edge select for external clock
Timer mode is selected by clearing the T0CS bit
(OPTION_REG<5>). In timer mode, the Timer0 mod-
ule (Figure 6-1) will increment every instruction cycle
(without prescaler). If the TMR0 register is written, the
increment is inhibited for the following two cycles
(Figure 6-2 and Figure 6-3). The user can work around
this by writing an adjusted value to the TMR0 register.
Counter mode is selected by setting the T0CS bit
(OPTION_REG<5>). In this mode TMR0 will increment
either on every rising or falling edge of pin RA4/T0CKI.
The incrementing edge is determined by the T0 source
edge select bit, T0SE (OPTION_REG<4>). Clearing bit
T0SE selects the rising edge. Restrictions on the exter-
nal clock input are discussed in detail in Section 6.2.
The prescaler is shared between the Timer0 Module
and the Watchdog Timer. The prescaler assignment is
controlled,
in
software,
by
control
bit
PSA
(OPTION_REG<3>). Clearing bit PSA will assign the
prescaler to the Timer0 Module. The prescaler is not
readable or writable. When the prescaler (Section 6.3)
is assigned to the Timer0 Module, the prescale value
(1:2, 1:4, ..., 1:256) is software selectable.
6.1
TMR0 Interrupt
The TMR0 interrupt is generated when the TMR0
register overflows from FFh to 00h. This overflow sets
the T0IF bit (INTCON<2>). The interrupt can be
masked by clearing enable bit T0IE (INTCON<5>). The
T0IF bit must be cleared in software by the Timer0
Module interrupt service routine before re-enabling this
interrupt. The TMR0 interrupt (Figure 6-4) cannot wake
the processor from SLEEP since the timer is shut off
during SLEEP.
FIGURE 6-1:
TMR0 BLOCK DIAGRAM
FIGURE 6-2:
TMR0 TIMING: INTERNAL CLOCK/NO PRESCALER
Note 1: Bits T0CS, T0SE, PS2, PS1, PS0 and PSA are located in the OPTION_REG register.
2: The prescaler is shared with the Watchdog Timer (Figure 6-6)
RA4/T0CKI
T0SE
0
1
0
pin
T0CS
FOSC/4
Programmable
Prescaler
Sync with
Internal
clocks
TMR0 register
PSout
(2 cycle delay)
PSout
Data bus
8
Set bit T0IF
on Overflow
PSA
PS2, PS1, PS0
3
PC-1
Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4
PC
Instruction
Fetch
TMR0
PC
PC+1
PC+2
PC+3
PC+4
PC+5
PC+6
T0
T0+1
T0+2
NT0
NT0+1
NT0+2
T0
MOVWF TMR0
MOVF TMR0,W
Write TMR0
executed
Read TMR0
reads NT0
Read TMR0
reads NT0
Read TMR0
reads NT0
Read TMR0
reads NT0 + 1
Read TMR0
reads NT0 + 2
Instruction
Executed
相关PDF资料
DSPIC30F1010-30I/MM IC DSPIC MCU/DSP 6K 28QFN
52745-1696 CONN FFC 16POS .5MM R/A ZIF SMD
52746-1470 CONN FFC 14POS .5MM R/A ZIF SMD
TS80C31X2-LIE IC MCU 8BIT 30/20MHZ 44-VQFP
TS87C54X2-MCE IC MCU 8BIT 16K OTP 40MHZ 44VQFP
PIC18F66K90-I/MR IC MCU 8BIT 64KB FLASH 64QFN
PIC24HJ32GP304-I/ML IC PIC MCU FLASH 32K 44-QFN
PIC18F67K22-I/PTRSL MCU PIC 128K FLASH XLP 64TQFP
相关代理商/技术参数
PIC16LF84A-04/P 制造商:Microchip Technology Inc 功能描述:8-Bit Microcontroller IC
PIC16LF84A-04/P 制造商:Microchip Technology Inc 功能描述:IC 8BIT FLASH MCU 制造商:Microchip Technology Inc 功能描述:IC, 8BIT FLASH MCU
PIC16LF84A-04/SO 功能描述:8位微控制器 -MCU 1.75KB 68 RAM 13 I/O RoHS:否 制造商:Silicon Labs 核心:8051 处理器系列:C8051F39x 数据总线宽度:8 bit 最大时钟频率:50 MHz 程序存储器大小:16 KB 数据 RAM 大小:1 KB 片上 ADC:Yes 工作电源电压:1.8 V to 3.6 V 工作温度范围:- 40 C to + 105 C 封装 / 箱体:QFN-20 安装风格:SMD/SMT
PIC16LF84A-04/SS 功能描述:8位微控制器 -MCU 1.75KB 68 RAM 13 I/O RoHS:否 制造商:Silicon Labs 核心:8051 处理器系列:C8051F39x 数据总线宽度:8 bit 最大时钟频率:50 MHz 程序存储器大小:16 KB 数据 RAM 大小:1 KB 片上 ADC:Yes 工作电源电压:1.8 V to 3.6 V 工作温度范围:- 40 C to + 105 C 封装 / 箱体:QFN-20 安装风格:SMD/SMT
PIC16LF84A-04/SS 制造商:Microchip Technology Inc 功能描述:8BIT FLASH MCU SMD 16LF84 SSOP20
PIC16LF84A-04I/P 功能描述:8位微控制器 -MCU 1.75KB 68 RAM 13 I/O RoHS:否 制造商:Silicon Labs 核心:8051 处理器系列:C8051F39x 数据总线宽度:8 bit 最大时钟频率:50 MHz 程序存储器大小:16 KB 数据 RAM 大小:1 KB 片上 ADC:Yes 工作电源电压:1.8 V to 3.6 V 工作温度范围:- 40 C to + 105 C 封装 / 箱体:QFN-20 安装风格:SMD/SMT
PIC16LF84A-04I/P 制造商:Microchip Technology Inc 功能描述:IC 8BIT FLASH MCU 16LF84 DIP18
PIC16LF84A-04I/SO 功能描述:8位微控制器 -MCU 1.75KB 68 RAM 13 I/O RoHS:否 制造商:Silicon Labs 核心:8051 处理器系列:C8051F39x 数据总线宽度:8 bit 最大时钟频率:50 MHz 程序存储器大小:16 KB 数据 RAM 大小:1 KB 片上 ADC:Yes 工作电源电压:1.8 V to 3.6 V 工作温度范围:- 40 C to + 105 C 封装 / 箱体:QFN-20 安装风格:SMD/SMT