AT90CAN32-16AUR Atmel, AT90CAN32-16AUR Datasheet - Page 231

• Manufacturer Part Number: AT90CAN32-16AUR
• Description: MCU AVR 32K FLASH 16MHZ 64-TQFP
• Manufacturer: Atmel
• Series: AVR® 90CANr

Specifications of AT90CAN32-16AUR

• Core Processor: AVR
• Core Size: 8-Bit
• Speed: 16MHz
• Connectivity: CAN, EBI/EMI, I²C, SPI, UART/USART
• Peripherals: Brown-out Detect/Reset, POR, PWM, WDT
• Number Of I /o: 53
• Program Memory Size: 32KB (32K x 8)
• Program Memory Type: FLASH
• Eeprom Size: 1K x 8
• Ram Size: 2K x 8
• Voltage - Supply (vcc/vdd): 2.7 V ~ 5.5 V
• Data Converters: A/D 8x10b
• Oscillator Type: Internal
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 64-TQFP, 64-VQFP
• Data Bus Width: 8 bit
• Mounting Style: SMD/SMT
• For Use With: ATSTK600 - DEV KIT FOR AVR/AVR32ATDVK90CAN1 - KIT DEV FOR AT90CAN128 MCU
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

18.8.6
7679H–CAN–08/08
Combining Several TWI Modes
In some cases, several TWI modes must be combined in order to complete the desired action.
Consider for example reading data from a serial EEPROM. Typically, such a transfer involves
the following steps:
Note that data is transmitted both from master to slave and vice versa. The master must instruct
the slave what location it wants to read, requiring the use of the MT mode. Subsequently, data
must be read from the slave, implying the use of the MR mode. Thus, the transfer direction must
be changed. The master must keep control of the bus during all these steps, and the steps
should be carried out as an atomical operation. If this principle is violated in a multimaster sys-
tem, another master can alter the data pointer in the EEPROM between steps 2 and 3, and the
master will read the wrong data location. Such a change in transfer direction is accomplished by
transmitting a REPEATED START between the transmission of the address byte and reception
of the data. After a REPEATED START, the master keeps ownership of the bus. The following
figure shows the flow in this transfer.
Figure 18-19. Combining Several TWI Modes to Access a Serial EEPROM
1. The transfer must be initiated
2. The EEPROM must be instructed what location should be read
3. The reading must be performed
4. The transfer must be finished
S
S = START
Transmitted from master to slave
SLA+W
A
Master Transmitter
ADDRESS
A
Rs = REPEATED START
Rs
Transmitted from slave to master
SLA+R
AT90CAN32/64/128
A
Master Receiver
DATA
P = STOP
A
231
P