參數(shù)資料
型號： PIC18LF2520-I/SP
廠商： Microchip Technology
文件頁數(shù)： 9/151頁
文件大?。?/td> 0K
描述： IC MCU FLASH 16KX16 28-DIP
產(chǎn)品培訓模塊： Asynchronous Stimulus
標準包裝： 15
系列： PIC® 18F
核心處理器： PIC
芯體尺寸： 8-位
速度： 40MHz
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： 32KB（16K x 16）
程序存儲器類型： 閃存
EEPROM 大?。?/td> 256 x 8
RAM 容量： 1.5K x 8
電壓 - 電源 (Vcc/Vdd)： 2 V ~ 5.5 V
數(shù)據(jù)轉(zhuǎn)換器： A/D 10x10b
振蕩器型： 內(nèi)部
工作溫度： -40°C ~ 85°C
封裝/外殼： 28-DIP（0.300"，7.62mm）
包裝： 管件
產(chǎn)品目錄頁面： 643 (CN2011-ZH PDF)
2011-2012 Microchip Technology Inc.
Preliminary
DS41579C-page 277
PIC16(L)F1782/3
When one device is transmitting a logical one, or letting
the line float, and a second device is transmitting a log-
ical zero, or holding the line low, the first device can
detect that the line is not a logical one. This detection,
when used on the SCL line, is called clock stretching.
Clock stretching gives slave devices a mechanism to
control the flow of data. When this detection is used on
the SDA line, it is called arbitration. Arbitration ensures
that there is only one master device communicating at
any single time.
26.3.1
CLOCK STRETCHING
When a slave device has not completed processing
data, it can delay the transfer of more data through the
process of clock stretching. An addressed slave device
may hold the SCL clock line low after receiving or send-
ing a bit, indicating that it is not yet ready to continue.
The master that is communicating with the slave will
attempt to raise the SCL line in order to transfer the
next bit, but will detect that the clock line has not yet
been released. Because the SCL connection is
open-drain, the slave has the ability to hold that line low
until it is ready to continue communicating.
Clock stretching allows receivers that cannot keep up
with a transmitter to control the flow of incoming data.
26.3.2
ARBITRATION
Each master device must monitor the bus for Start and
Stop bits. If the device detects that the bus is busy, it
cannot begin a new message until the bus returns to an
Idle state.
However, two master devices may try to initiate a trans-
mission on or about the same time. When this occurs,
the process of arbitration begins. Each transmitter
checks the level of the SDA data line and compares it
to the level that it expects to find. The first transmitter to
observe that the two levels do not match, loses arbitra-
tion, and must stop transmitting on the SDA line.
For example, if one transmitter holds the SDA line to a
logical one (lets it float) and a second transmitter holds
it to a logical zero (pulls it low), the result is that the
SDA line will be low. The first transmitter then observes
that the level of the line is different than expected and
concludes that another transmitter is communicating.
The first transmitter to notice this difference is the one
that loses arbitration and must stop driving the SDA
line. If this transmitter is also a master device, it also
must stop driving the SCL line. It then can monitor the
lines for a Stop condition before trying to reissue its
transmission. In the meantime, the other device that
has not noticed any difference between the expected
and actual levels on the SDA line continues with its
original transmission. It can do so without any compli-
cations, because so far, the transmission appears
exactly as expected with no other transmitter disturbing
the message.
Slave Transmit mode can also be arbitrated, when a
master addresses multiple slaves, but this is less com-
mon.
If two master devices are sending a message to two dif-
ferent slave devices at the address stage, the master
sending the lower slave address always wins arbitra-
tion. When two master devices send messages to the
same slave address, and addresses can sometimes
refer to multiple slaves, the arbitration process must
continue into the data stage.
Arbitration usually occurs very rarely, but it is a neces-
sary process for proper multi-master support.
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PIC18LF2520T-I/SO 功能描述:8位微控制器 -MCU 32KB 1536 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
PIC18LF2523-I/ML 功能描述:8位微控制器 -MCU 32KB 1536bytes-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
PIC18LF2523-I/SO 功能描述:8位微控制器 -MCU 32KB 1536bytes-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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