130
8008H–AVR–04/11
ATtiny48/88
15.3.1
TWI Terminology
The following definitions are frequently encountered in this section.
The PRTWI bit in “PRR – Power Reduction Register” on page 40 must be written to zero to
enable the 2-wire Serial Interface.
15.3.2
Electrical Interconnection
As depicted in Figure 15-1, both bus lines are connected to the positive supply voltage through
pull-up resistors. The bus drivers of all TWI-compliant devices are open-drain or open-collector.
This implements a wired-AND function which is essential to the operation of the interface. A low
level on a TWI bus line is generated when one or more TWI devices output a zero. A high level
is output when all TWI devices tri-state their outputs, allowing the pull-up resistors to pull the line
high. Note that all AVR devices connected to the TWI bus must be powered in order to allow any
bus operation.
The number of devices that can be connected to the bus is only limited by the bus capacitance
limit of 400 pF and the 7-bit slave address space. A detailed specification of the electrical char-
acteristics of the TWI is given in “Two-Wire Serial Interface Characteristics” on page 212. Two
different sets of specifications are presented there, one relevant for bus speeds below 100 kHz,
and one valid for bus speeds up to 400 kHz.
15.4
Data Transfer and Frame Format
15.4.1
Transferring Bits
Each data bit transferred on the TWI bus is accompanied by a pulse on the clock line. The level
of the data line must be stable when the clock line is high. The only exception to this rule is for
generating start and stop conditions.
Figure 15-2. Data Validity
Table 15-1.
TWI Terminology
Term
Description
Master
The device that initiates and terminates a transmission and generates the SCL clock.
Slave
The device addressed by a Master.
Transmitter
The device placing data on the bus.
Receiver
The device reading data from the bus.
SDA
SCL
Data Stable
Data Change
相关PDF资料
PIC16F87-E/ML IC MCU FLASH 4KX14 EEPROM 28QFN
PIC18LF4320-I/ML IC MCU FLASH 4KX16 EEPROM 44QFN
PIC16F77T-I/PTG IC MCU FLASH 8KX14 W/AD 44TQFP
PIC16LF1933-I/SO IC PIC MCU FLASH 4K 28-SOIC
PIC16C54C-20I/SO IC MCU OTP 512X12 18SOIC
PIC16LF726-I/SO IC PIC MCU FLASH 8K 1.8V 28-SOIC
PIC12CE673-10/P IC MCU OTP 1KX14 A/D&EE 8DIP
PIC16F726-I/SO IC PIC MCU FLASH 8KX14 28-SOIC
相关代理商/技术参数
PIC16F87T-E/SO 功能描述:8位微控制器 -MCU 20MHz 4K Flash 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
PIC16F87T-E/SS 功能描述:8位微控制器 -MCU 20MHz 4K Flash 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
PIC16F87T-I/ML 功能描述:8位微控制器 -MCU 7KB 368 RAM 16 I/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
PIC16F87T-I/SO 功能描述:8位微控制器 -MCU 7KB 368 RAM 16 I/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
PIC16F87T-I/SS 功能描述:8位微控制器 -MCU 7KB 368 RAM 16 I/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
PIC16F882-E/ML 功能描述:8位微控制器 -MCU 3.5KB Enh FLSH 128 RAM 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
PIC16F882-E/SO 功能描述:8位微控制器 -MCU 3.5KB Enh FLSH 128 RAM 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
PIC16F882-E/SP 功能描述:8位微控制器 -MCU 3.5KB Enh FLSH 128 RAM 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