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参数资料
| 型号： | MQ83C154DTXXX-16/883 |
| 厂商： | ATMEL CORP |
| 元件分类： | 微控制器/微处理器 |
| 英文描述： | 8-BIT, MROM, 16 MHz, MICROCONTROLLER, CQFP44 |
| 封装： | CERAMIC, QFP-44 |
| 文件页数： | 15/132页 |
| 文件大小： | 10886K |
| 代理商： | MQ83C154DTXXX-16/883 |
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185
ATmega8535(L)
2502K–AVR–10/06
Using the TWI
The AVR TWI is byte-oriented and interrupt based. Interrupts are issued after all bus
events, like reception of a byte or transmission of a START condition. Because the TWI
is interrupt-based, the application software is free to carry on other operations during a
TWI byte transfer. Note that the TWI Interrupt Enable (TWIE) bit in TWCR together with
the Global Interrupt Enable bit in SREG allow the application to decide whether or not
assertion of the TWINT Flag should generate an interrupt request. If the TWIE bit is
cleared, the application must poll the TWINT Flag in order to detect actions on the TWI
bus.
When the TWINT Flag is asserted, the TWI has finished an operation and awaits appli-
cation response. In this case, the TWI Status Register (TWSR) contains a value
indicating the current state of the TWI bus. The application software can then decide
how the TWI should behave in the next TWI bus cycle by manipulating the TWCR and
TWDR Registers.
Figure 85 is a simple example of how the application can interface to the TWI hardware.
In this example, a Master wishes to transmit a single data byte to a Slave. This descrip-
tion is quite abstract, a more detailed explanation follows later in this section. A simple
code example implementing the desired behavior is also presented.
Figure 85. Interfacing the Application to the TWI in a Typical Transmission
1.
The first step in a TWI transmission is to transmit a START condition. This is
done by writing a specific value into TWCR, instructing the TWI hardware to
transmit a START condition. Which value to write is described later on. However,
it is important that the TWINT bit is set in the value written. Writing a one to
TWINT clears the flag. The TWI will not start any operation as long as the
TWINT bit in TWCR is set. Immediately after the application has cleared TWINT,
the TWI will initiate transmission of the START condition.
2.
When the START condition has been transmitted, the TWINT Flag in TWCR is
set, and TWSR is updated with a status code indicating that the START condition
has successfully been sent.
3.
The application software should now examine the value of TWSR, to make sure
that the START condition was successfully transmitted. If TWSR indicates other-
wise, the application software might take some special action, like calling an
error routine. Assuming that the status code is as expected, the application must
START
SLA+W
A
Data
A
STOP
1. Application writes
to TWCR to initiate
transmission of
START
2. TWINT set.
Status code indicates
START condition sent
4. TWINT set.
Status code indicates
SLA+W sent, ACK
received
6. TWINT set.
Status code indicates
data sent, ACK received
3. Check TWSR to see if START was
sent. Application loads SLA+W into
TWDR, and loads appropriate control
signals into TWCR, making sure that
TWINT is written to one, and TWSTA is
written to zero.
5. Check TWSR to see if SLA+W was
sent and ACK received. Application
loads data into TWDR, and loads
appropriate control signals into TWCR,
making sure that TWINT is
wwritten to one.
7. Check TWSR to see if data was sent
and ACK received. Application loads
appropriate control signals to send
STOP into TWCR, making sure that
TWINT is written to one.
TWI bus
Indicates
TWINT set
Application
Action
TWI
Hardw
are
Action
相关PDF资料 |
PDF描述 |
|---|---|
| MQ83C154DTXXX-16P883D | 8-BIT, MROM, 16 MHz, MICROCONTROLLER, CQFP44 |
| MD83C154DTXXX-20/883 | 8-BIT, MROM, 20 MHz, MICROCONTROLLER, CDIP40 |
| MR83C154DTXXX-20P883D | 8-BIT, MROM, 20 MHz, MICROCONTROLLER, CQCC44 |
| MR83C154DTXXX-20P883 | 8-BIT, MROM, 20 MHz, MICROCONTROLLER, CQCC44 |
| MR83C154DTXXX-25P883R | 8-BIT, MROM, 25 MHz, MICROCONTROLLER, CQCC44 |
相关代理商/技术参数 |
参数描述 |
|---|---|
| MQ83C154-L16 | 制造商:TEMIC 制造商全称:TEMIC Semiconductors 功能描述:CMOS 0 to 36 MHz Single Chip 8-bit Microcontroller |
| MQ83C154T-12 | 制造商:TEMIC 制造商全称:TEMIC Semiconductors 功能描述:CMOS 0 to 36 MHz Single Chip 8-bit Microcontroller |
| MQ83C154T-16 | 制造商:TEMIC 制造商全称:TEMIC Semiconductors 功能描述:CMOS 0 to 36 MHz Single Chip 8-bit Microcontroller |
| MQ83C154T-20 | 制造商:TEMIC 制造商全称:TEMIC Semiconductors 功能描述:CMOS 0 to 36 MHz Single Chip 8-bit Microcontroller |
| MQ83C154T-25 | 制造商:TEMIC 制造商全称:TEMIC Semiconductors 功能描述:CMOS 0 to 36 MHz Single Chip 8-bit Microcontroller |
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