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型号： PIC18F4420T-I/ML
厂商： Microchip Technology
文件页数： 26/151页
文件大小： 0K
描述： IC MCU FLASH 8KX16 44QFN
产品培训模块： Asynchronous Stimulus
标准包装： 1,600
系列： PIC® 18F
核心处理器： PIC
芯体尺寸： 8-位
速度： 40MHz
连通性： I²C，SPI，UART/USART
外围设备： 欠压检测/复位，HLVD，POR，PWM，WDT
输入/输出数： 36
程序存储器容量： 16KB（8K x 16）
程序存储器类型： 闪存
EEPROM 大小： 256 x 8
RAM 容量： 768 x 8
电压 - 电源 (Vcc/Vdd)： 4.2 V ~ 5.5 V
数据转换器： A/D 13x10b
振荡器型： 内部
工作温度： -40°C ~ 85°C
封装/外壳： 44-VQFN 裸露焊盘
包装： 带卷 (TR)
PIC16(L)F1782/3
DS41579C-page 294
Preliminary
2011-2012 Microchip Technology Inc.
26.5.6
CLOCK STRETCHING
Clock stretching occurs when a device on the bus
holds the SCL line low effectively pausing communica-
tion. The slave may stretch the clock to allow more
time to handle data or prepare a response for the mas-
ter device. A master device is not concerned with
stretching as anytime it is active on the bus and not
transferring data it is stretching. Any stretching done
by a slave is invisible to the master software and han-
dled by the hardware that generates SCL.
The CKP bit of the SSPCON1 register is used to con-
trol stretching in software. Any time the CKP bit is
cleared, the module will wait for the SCL line to go low
and then hold it. Setting CKP will release SCL and
allow more communication.
26.5.6.1
Normal Clock Stretching
Following an ACK if the R/W bit of SSPSTAT is set, a
read request, the slave hardware will clear CKP. This
allows the slave time to update SSPBUF with data to
transfer to the master. If the SEN bit of SSPCON2 is
set, the slave hardware will always stretch the clock
after the ACK sequence. Once the slave is ready; CKP
is set by software and communication resumes.
26.5.6.2
10-bit Addressing Mode
In 10-bit Addressing mode, when the UA bit is set the
clock is always stretched. This is the only time the SCL
is stretched without CKP being cleared. SCL is
released immediately after a write to SSPADD.
26.5.6.3
Byte NACKing
When AHEN bit of SSPCON3 is set; CKP is cleared by
hardware after the 8th falling edge of SCL for a
received matching address byte. When DHEN bit of
SSPCON3 is set; CKP is cleared after the 8th falling
edge of SCL for received data.
Stretching after the 8th falling edge of SCL allows the
slave to look at the received address or data and
decide if it wants to ACK the received data.
26.5.7
CLOCK SYNCHRONIZATION AND
THE CKP BIT
Any time the CKP bit is cleared, the module will wait
for the SCL line to go low and then hold it. However,
clearing the CKP bit will not assert the SCL output low
until the SCL output is already sampled low. There-
fore, the CKP bit will not assert the SCL line until an
external I2C master device has already asserted the
SCL line. The SCL output will remain low until the CKP
bit is set and all other devices on the I2C bus have
released SCL. This ensures that a write to the CKP bit
will not violate the minimum high time requirement for
SCL (see Figure 26-22).
FIGURE 26-23:
CLOCK SYNCHRONIZATION TIMING
Note 1:
The BF bit has no effect on if the clock will
be stretched or not. This is different than
previous versions of the module that
would not stretch the clock, clear CKP, if
SSPBUF was read before the 9th falling
edge of SCL.
2:
Previous versions of the module did not
stretch the clock for a transmission if
SSPBUF was loaded before the 9th fall-
ing edge of SCL. It is now always cleared
for read requests.
Note:
Previous versions of the module did not
stretch the clock if the second address byte
did not match.
SDA
SCL
DX
– 1
DX
WR
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
SSPCON1
CKP
Master device
releases clock
Master device
asserts clock
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PIC18F4423-E/ML 功能描述:8位微控制器 -MCU 16KB 768bytes-RAM 36I/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
PIC18F4423-E/P 功能描述:8位微控制器 -MCU 16KB 768bytes-RAM 36I/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
PIC18F4423-E/PT 功能描述:8位微控制器 -MCU 16KB 768bytes-RAM 36I/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
PIC18F4423-I/ML 功能描述:8位微控制器 -MCU 16KB 768bytes-RAM 36I/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
PIC18F4423-I/P 功能描述:8位微控制器 -MCU 16KB 768bytes-RAM 36I/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
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