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参数资料
| 型号： | PIC12C508AT-04/SN |
| 厂商： | Microchip Technology |
| 文件页数： | 34/113页 |
| 文件大小： | 0K |
| 描述： | IC MCU OTP 512X12 8SOIC |
| 产品培训模块： | Asynchronous Stimulus |
| 标准包装： | 3,300 |
| 系列： | PIC® 12C |
| 核心处理器： | PIC |
| 芯体尺寸： | 8-位 |
| 速度： | 4MHz |
| 外围设备： | POR，WDT |
| 输入/输出数： | 5 |
| 程序存储器容量： | 768B（512 x 12） |
| 程序存储器类型： | OTP |
| RAM 容量： | 25 x 8 |
| 电压 - 电源 (Vcc/Vdd)： | 3 V ~ 5.5 V |
| 振荡器型： | 内部 |
| 工作温度： | 0°C ~ 70°C |
| 封装/外壳： | 8-SOIC（0.154"，3.90mm 宽） |
| 包装： | 带卷 (TR) |
| 配用： | 309-1046-ND - ADAPTER 8-SOIC TO 8-DIP 309-1045-ND - ADAPTER 8-SOIC TO 8-DIP AC124001-ND - MODULE SKT PROMATEII 8DIP/SOIC |
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1999 Microchip Technology Inc.
DS40139E-page 27
PIC12C5XX
6.1
Using Timer0 with an External Clock
When an external clock input is used for Timer0, it
must meet certain requirements. The external clock
requirement is due to internal phase clock (TOSC)
synchronization. Also, there is a delay in the actual
incrementing of Timer0 after synchronization.
6.1.1
EXTERNAL CLOCK SYNCHRONIZATION
When no prescaler is used, the external clock input is
the same as the prescaler output. The synchronization
of
T0CKI
with
the
internal
phase
clocks
is
accomplished by sampling the prescaler output on the
Q2 and Q4 cycles of the internal phase clocks
(Figure 6-4). Therefore, it is necessary for T0CKI to be
high for at least 2TOSC (and a small RC delay of 20 ns)
and low for at least 2TOSC (and a small RC delay of
20 ns). Refer to the electrical specification of the
desired device.
When a prescaler is used, the external clock input is
divided by the asynchronous ripple counter-type
prescaler so that the prescaler output is symmetrical.
For
the
external
clock
to
meet
the
sampling
requirement, the ripple counter must be taken into
account. Therefore, it is necessary for T0CKI to have a
period of at least 4TOSC (and a small RC delay of
40 ns) divided by the prescaler value. The only
requirement on T0CKI high and low time is that they
do not violate the minimum pulse width requirement of
10 ns. Refer to parameters 40, 41 and 42 in the
electrical specification of the desired device.
6.1.2
TIMER0 INCREMENT DELAY
Since the prescaler output is synchronized with the
internal clocks, there is a small delay from the time the
external clock edge occurs to the time the Timer0
module is actually incremented. Figure 6-4 shows the
delay from the external clock edge to the timer
incrementing.
6.1.3
OPTION REGISTER EFFECT ON GP2 TRIS
If the option register is set to read TIMER0 from the pin,
the port is forced to an input regardless of the TRIS reg-
ister setting.
FIGURE 6-4:
TIMER0 TIMING WITH EXTERNAL CLOCK
Increment Timer0 (Q4)
External Clock Input or
Q1
Q2
Q3 Q4
Q1
Q2
Q3 Q4
Q1
Q2
Q3 Q4
Q1
Q2
Q3 Q4
Timer0
T0
T0 + 1
T0 + 2
Small pulse
misses sampling
External Clock/Prescaler
Output After Sampling
(3)
Note 1:
2:
3:
Delay from clock input change to Timer0 increment is 3Tosc to 7Tosc. (Duration of Q = Tosc).
Therefore, the error in measuring the interval between two edges on Timer0 input =
± 4Tosc max.
External clock if no prescaler selected, Prescaler output otherwise.
The arrows indicate the points in time where sampling occurs.
Prescaler Output (2)
(1)
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相关代理商/技术参数 |
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|---|---|
| PIC12C508T | 制造商:MICROCHIP 制造商全称:Microchip Technology 功能描述:8-Pin, 8-Bit CMOS Microcontroller |
| PIC12C508T-04/EJW | 制造商:MICROCHIP 制造商全称:Microchip Technology 功能描述:8-Pin, 8-Bit CMOS Microcontrollers |
| PIC12C508T-04/EP | 制造商:MICROCHIP 制造商全称:Microchip Technology 功能描述:8-Pin, 8-Bit CMOS Microcontrollers |
| PIC12C508T-04/ESM | 制造商:MICROCHIP 制造商全称:Microchip Technology 功能描述:8-Pin, 8-Bit CMOS Microcontrollers |
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