參數(shù)資料
型號： PIC18F2420-E/ML
廠商： Microchip Technology
文件頁數(shù)： 26/151頁
文件大小： 0K
描述： IC PIC MCU FLASH 8KX16 28QFN
產品培訓模塊： Asynchronous Stimulus
PIC18 J Series MCU Overview
標準包裝： 61
系列： PIC® 18F
核心處理器： PIC
芯體尺寸： 8-位
速度： 25MHz
連通性： I²C，SPI，UART/USART
外圍設備： 欠壓檢測/復位，HLVD，POR，PWM，WDT
輸入/輸出數(shù)： 25
程序存儲器容量： 16KB（8K x 16）
程序存儲器類型： 閃存
EEPROM 大?。?/td> 256 x 8
RAM 容量： 768 x 8
電壓 - 電源 (Vcc/Vdd)： 4.2 V ~ 5.5 V
數(shù)據(jù)轉換器： A/D 10x10b
振蕩器型： 內部
工作溫度： -40°C ~ 125°C
封裝/外殼： 28-VQFN 裸露焊盤
包裝： 管件
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
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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PIC18F2420-I/ML 功能描述:8位微控制器 -MCU 16kBF 768RM 25I/O RoHS:否 制造商:Silicon Labs 核心:8051 處理器系列:C8051F39x 數(shù)據(jù)總線寬度:8 bit 最大時鐘頻率:50 MHz 程序存儲器大小:16 KB 數(shù)據(jù) RAM 大小:1 KB 片上 ADC:Yes 工作電源電壓:1.8 V to 3.6 V 工作溫度范圍:- 40 C to + 105 C 封裝 / 箱體:QFN-20 安裝風格:SMD/SMT
PIC18F2420-I/SO 功能描述:8位微控制器 -MCU 16KB 768 RAM 25I/O RoHS:否 制造商:Silicon Labs 核心:8051 處理器系列:C8051F39x 數(shù)據(jù)總線寬度:8 bit 最大時鐘頻率:50 MHz 程序存儲器大小:16 KB 數(shù)據(jù) RAM 大小:1 KB 片上 ADC:Yes 工作電源電壓:1.8 V to 3.6 V 工作溫度范圍:- 40 C to + 105 C 封裝 / 箱體:QFN-20 安裝風格:SMD/SMT
PIC18F2420-I/SOG 制造商:Microchip Technology 功能描述:MCU 8-Bit PIC18 PIC RISC 16KB Flash 5V 28-Pin SOIC W Tube
PIC18F2420-I/SP 功能描述:8位微控制器 -MCU 16KB 768 RAM 25I/O RoHS:否 制造商:Silicon Labs 核心:8051 處理器系列:C8051F39x 數(shù)據(jù)總線寬度:8 bit 最大時鐘頻率:50 MHz 程序存儲器大小:16 KB 數(shù)據(jù) RAM 大小:1 KB 片上 ADC:Yes 工作電源電壓:1.8 V to 3.6 V 工作溫度范圍:- 40 C to + 105 C 封裝 / 箱體:QFN-20 安裝風格:SMD/SMT
PIC18F2420T-I/ML 功能描述:8位微控制器 -MCU 16KB 768 RAM 25I/O RoHS:否 制造商:Silicon Labs 核心:8051 處理器系列:C8051F39x 數(shù)據(jù)總線寬度:8 bit 最大時鐘頻率:50 MHz 程序存儲器大小:16 KB 數(shù)據(jù) RAM 大小:1 KB 片上 ADC:Yes 工作電源電壓:1.8 V to 3.6 V 工作溫度范圍:- 40 C to + 105 C 封裝 / 箱體:QFN-20 安裝風格:SMD/SMT
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