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ATMEGA2560-16AU-SL383 参数 Datasheet PDF下载

ATMEGA2560-16AU-SL383图片预览
型号: ATMEGA2560-16AU-SL383
PDF下载: 下载PDF文件 查看货源
内容描述: [Microcontroller, 8-Bit, FLASH, AVR RISC CPU, 16MHz, CMOS, PQFP100, 14 X 14 MM, 1 MM HEIGHT, 0.50 MM PITCH, GREEN, PLASTIC, MS-026AED, TQFP-100]
分类和应用: 时钟微控制器
文件页数/大小: 448 页 / 7518 K
品牌: ATMEL [ ATMEL ]
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Figure 24-12. Data Transfer in Master Receiver Mode  
VCC  
Device 1  
MASTER  
RECEIVER  
Device 2  
SLAVE  
TRANSMITTER  
Device 3  
Device n  
R1  
R2  
........  
SDA  
SCL  
A START condition is sent by writing the following value to TWCR:  
TWCR  
TWINT  
TWEA  
TWSTA  
TWSTO  
TWWC  
TWEN  
TWIE  
value  
1
X
1
0
X
1
0
X
TWEN must be written to one to enable the 2-wire Serial Interface, TWSTA must be written to  
one to transmit a START condition and TWINT must be set to clear the TWINT Flag. The TWI  
will then test the 2-wire Serial Bus and generate a START condition as soon as the bus  
becomes free. After a START condition has been transmitted, the TWINT Flag is set by hard-  
ware, and the status code in TWSR will be 0x08 (See Table 24-1). In order to enter MR mode,  
SLA+R must be transmitted. This is done by writing SLA+R to TWDR. Thereafter the TWINT bit  
should be cleared (by writing it to one) to continue the transfer. This is accomplished by writing  
the following value to TWCR:  
TWCR  
TWINT  
TWEA  
TWSTA  
TWSTO  
TWWC  
TWEN  
TWIE  
value  
1
X
0
0
X
1
0
X
When SLA+R have been transmitted and an acknowledgement bit has been received, TWINT is  
set again and a number of status codes in TWSR are possible. Possible status codes in Master  
mode are 0x38, 0x40, or 0x48. The appropriate action to be taken for each of these status codes  
is detailed in Table 24-2. Received data can be read from the TWDR Register when the TWINT  
Flag is set high by hardware. This scheme is repeated until the last byte has been received.  
After the last byte has been received, the MR should inform the ST by sending a NACK after the  
last received data byte. The transfer is ended by generating a STOP condition or a repeated  
START condition. A STOP condition is generated by writing the following value to TWCR:  
TWCR  
TWINT  
TWEA  
TWSTA  
TWSTO  
TWWC  
TWEN  
TWIE  
value  
1
X
0
1
X
1
0
X
A REPEATED START condition is generated by writing the following value to TWCR:  
TWCR  
TWINT  
TWEA  
TWSTA  
TWSTO  
TWWC  
TWEN  
TWIE  
value  
1
X
1
0
X
1
0
X
After a repeated START condition (state 0x10) the 2-wire Serial Interface can access the same  
Slave again, or a new Slave without transmitting a STOP condition. Repeated START enables  
256  
ATmega640/1280/1281/2560/2561  
2549L–AVR–08/07  
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