ATmega1284RZAP Atmel Corporation, ATmega1284RZAP Datasheet - Page 218

• Manufacturer Part Number: ATmega1284RZAP
• Manufacturer: Atmel Corporation

Specifications of ATmega1284RZAP

• Flash (kbytes): 128 Kbytes
• Max. Operating Frequency: 20 MHz
• Max I/o Pins: 32
• Spi: 3
• Twi (i2c): 1
• Uart: 2
• Adc Channels: 8
• Adc Resolution (bits): 10
• Adc Speed (ksps): 15
• Analog Comparators: 1
• Crypto Engine: No
• Sram (kbytes): 16
• Eeprom (bytes): 4096
• Operating Voltage (vcc): 1.8 to 3.6
• Timers: 3
• Frequency Band: 2.4 GHz
• Max Data Rate (mb/s): 0.25
• Antenna Diversity: No
• External Pa Control: No
• Power Output (dbm): 3
• Receiver Sensitivity (dbm): -101
• Receive Current Consumption (ma): 16.0
• Transmit Current Consumption (ma): 17.0
• Link Budget (dbm): 104

19.7
8059D–AVR–11/09
6
7
Assembly Code Example
wait3:
in
sbrs r16,TWINT
rjmp wait3
in
andi r16, 0xF8
cpi
brne ERROR
ldi
out
Transmission Modes
r16,TWCR
r16,TWSR
r16, MT_DATA_ACK
r16, (1<<TWINT)|(1<<TWEN)|
(1<<TWSTO)
TWCR, r16
The TWI can operate in one of four major modes. These are named Master Transmitter (MT),
Master Receiver (MR), Slave Transmitter (ST) and Slave Receiver (SR). Several of these
modes can be used in the same application. As an example, the TWI can use MT mode to write
data into a TWI EEPROM, MR mode to read the data back from the EEPROM. If other masters
are present in the system, some of these might transmit data to the TWI, and then SR mode
would be used. It is the application software that decides which modes are legal.
The following sections describe each of these modes. Possible status codes are described
along with figures detailing data transmission in each of the modes. These figures contain the
following abbreviations:
S: START condition
Rs: REPEATED START condition
R: Read bit (high level at SDA)
W: Write bit (low level at SDA)
A: Acknowledge bit (low level at SDA)
A: Not acknowledge bit (high level at SDA)
Data: 8-bit data byte
P: STOP condition
SLA: Slave Address
In
TWINT Flag is set. The numbers in the circles show the status code held in TWSR, with the
prescaler bits masked to zero. At these points, actions must be taken by the application to con-
tinue or complete the TWI transfer. The TWI transfer is suspended until the TWINT Flag is
cleared by software.
When the TWINT Flag is set, the status code in TWSR is used to determine the appropriate soft-
ware action. For each status code, the required software action and details of the following serial
transfer are given in
bits are masked to zero in these tables.
Figure 19-12 on page 221
Table 19-2 on page 220
C Example
while (!(TWCR & (1<<TWINT)))
if ((TWSR & 0xF8) !=
MT_DATA_ACK)
TWCR = (1<<TWINT)|(1<<TWEN)|
(1<<TWSTO);
to
;
ERROR();
Figure 19-18 on page
to
Table 19-5 on page
230, circles are used to indicate that the
Comments
Wait for TWINT Flag set. This
indicates that the DATA has been
transmitted, and ACK/NACK has
been received.
Check value of TWI Status
Register. Mask prescaler bits. If
status different from
MT_DATA_ACK go to ERROR
Transmit STOP condition
229. Note that the prescaler
ATmega1284P
218