参数资料
型号: MC68HC705SR3CPE
厂商: Freescale Semiconductor
文件页数: 42/96页
文件大小: 0K
描述: IC MCU 3.75K 2.1MHZ OTP 40-DIP
标准包装: 9
系列: HC05
核心处理器: HC05
芯体尺寸: 8-位
速度: 4MHz
外围设备: LED,POR
输入/输出数: 32
程序存储器容量: 3.75KB(3.75K x 8)
程序存储器类型: OTP
RAM 容量: 192 x 8
电压 - 电源 (Vcc/Vdd): 3 V ~ 5.5 V
数据转换器: A/D 4x8b
振荡器型: 内部
工作温度: -40°C ~ 85°C
封装/外壳: 40-DIP(0.600",15.24mm)
包装: 管件
MC68HC05SR3
Freescale
6-1
TIMER
6
TIMER
This section describes the operation of the 8-bit count-down timer in the MC68HC05SR3.
6.1
Timer Overview
The MC68HC05SR3 timer block diagram is shown in Figure 6-1. The timer contains a single 8-bit
software programmable count-down counter with a 7-bit software selectable prescaler. The
counter may be preset under software control and decrements towards zero. When the counter
decrements to zero, the timer interrupt flag (TIF bit in Timer Control Register, TCR) is set. Once
timer interrupt flag is set, an interrupt is generated to the CPU only if the TIM bit in the TCR and
I-bit in the CCR are cleared. When a interrupt is recognized, after completion of the current
instruction, the processor proceeds to store the appropriate registers on the stack and then
fetches the timer interrupt vector from locations $1FF6 and $1FF7.
The counter continues to count after it reaches zero, allowing the software to determine the
number of internal or external clocks since the timer interrupt flag was set. The counter may be
read at any time by the processor without disturbing the count. The contents of the counter
become stable prior to the read portion of a cycle and do not change during the read. The timer
interrupt flag remains set until cleared by the software. If a write occurs before the timer interrupt
is served, the interrupt is lost. The timer interrupt flag may also be used as a scanned status bit in
a non-interrupt mode of operation.
The prescaler is a 7-bit divider which is used to extend the maximum length of the timer. Bit 0, 1,
2 (PR0, PR1, PR2) of TCR are programmed to choose the appropriate prescaler output which is
used as the 8-bit counter clock input. The processor cannot write into or read from the prescaler;
however, its contents can be cleared to all zeros by writing to the PRER bit in the TCR. This will
allow for truncation-free counting.
The input clock for the timer sub-system is selectable from internal, external, or a combination of
internal and external sources. The TCEX and TINE bits in the Timer Control Register selects the
timer input clock.
TPG
45
05SR3.Book Page 1 Thursday, August 4, 2005 1:08 PM
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MC68HC705SR3CPE 制造商:Freescale Semiconductor 功能描述:8-Bit Microcontroller IC
MC68HC705SR3PE 功能描述:IC MCU 3.75K 2.1MHZ OTP 40-DIP RoHS:是 类别:集成电路 (IC) >> 嵌入式 - 微控制器, 系列:HC05 标准包装:1 系列:AVR® ATmega 核心处理器:AVR 芯体尺寸:8-位 速度:16MHz 连通性:I²C,SPI,UART/USART 外围设备:欠压检测/复位,POR,PWM,WDT 输入/输出数:32 程序存储器容量:32KB(16K x 16) 程序存储器类型:闪存 EEPROM 大小:1K x 8 RAM 容量:2K x 8 电压 - 电源 (Vcc/Vdd):2.7 V ~ 5.5 V 数据转换器:A/D 8x10b 振荡器型:内部 工作温度:-40°C ~ 125°C 封装/外壳:44-TQFP 包装:剪切带 (CT) 其它名称:ATMEGA324P-B15AZCT
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