ATMEGA16A-PU Atmel, ATMEGA16A-PU Datasheet - Page 179

MCU AVR 16K FLASH 16MHZ 40-PDIP

ATMEGA16A-PU

Manufacturer Part Number
ATMEGA16A-PU
Description
MCU AVR 16K FLASH 16MHZ 40-PDIP
Manufacturer
Atmel
Series
AVR® ATmegar
Datasheets

Specifications of ATMEGA16A-PU

Core Processor
AVR
Core Size
8-Bit
Speed
16MHz
Connectivity
I²C, SPI, UART/USART
Peripherals
Brown-out Detect/Reset, POR, PWM, WDT
Number Of I /o
32
Program Memory Size
16KB (8K x 16)
Program Memory Type
FLASH
Eeprom Size
512 x 8
Ram Size
1K 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
40-DIP (0.600", 15.24mm)
Processor Series
ATMEGA16x
Core
AVR8
Data Bus Width
8 bit
Data Ram Size
1 KB
Interface Type
2-Wire/SPI/USART
Maximum Clock Frequency
16 MHz
Number Of Programmable I/os
32
Number Of Timers
3
Maximum Operating Temperature
+ 85 C
Mounting Style
Through Hole
3rd Party Development Tools
EWAVR, EWAVR-BL
Development Tools By Supplier
ATAVRDRAGON, ATSTK500, ATSTK600, ATAVRISP2, ATAVRONEKIT
Minimum Operating Temperature
- 40 C
On-chip Adc
8-ch x 10-bit
Package
40PDIP
Device Core
AVR
Family Name
ATmega
Maximum Speed
16 MHz
Operating Supply Voltage
3.3|5 V
Controller Family/series
AVR MEGA
No. Of I/o's
32
Eeprom Memory Size
512Byte
Ram Memory Size
1KB
Cpu Speed
16MHz
Rohs Compliant
Yes
For Use With
ATSTK600 - DEV KIT FOR AVR/AVR32ATSTK500 - PROGRAMMER AVR STARTER KIT
Lead Free Status / RoHS Status
Lead free / RoHS Compliant
20.4
8154B–AVR–07/09
Multi-master Bus Systems, Arbitration and Synchronization
Figure 20-6. Typical Data Transmission
The TWI protocol allows bus systems with several Masters. Special concerns have been taken
in order to ensure that transmissions will proceed as normal, even if two or more Masters initiate
a transmission at the same time. Two problems arise in multi-master systems:
The wired-ANDing of the bus lines is used to solve both these problems. The serial clocks from
all Masters will be wired-ANDed, yielding a combined clock with a high period equal to the one
from the Master with the shortest high period. The low period of the combined clock is equal to
the low period of the Master with the longest low period. Note that all Masters listen to the SCL
line, effectively starting to count their SCL high and low time-out periods when the combined
SCL line goes high or low, respectively.
Figure 20-7. SCL Synchronization between Multiple Masters
Arbitration is carried out by all Masters continuously monitoring the SDA line after outputting
data. If the value read from the SDA line does not match the value the Master had output, it has
lost the arbitration. Note that a Master can only lose arbitration when it outputs a high SDA value
while another Master outputs a low value. The losing Master should immediately go to Slave
• An algorithm must be implemented allowing only one of the Masters to complete the
• Different Masters may use different SCL frequencies. A scheme must be devised to
transmission. All other Masters should cease transmission when they discover that they have
lost the selection process. This selection process is called arbitration. When a contending
Master discovers that it has lost the arbitration process, it should immediately switch to Slave
mode to check whether it is being addressed by the winning Master. The fact that multiple
Masters have started transmission at the same time should not be detectable to the Slaves,
i.e., the data being transferred on the bus must not be corrupted.
synchronize the serial clocks from all Masters, in order to let the transmission proceed in a
lockstep fashion. This will facilitate the arbitration process.
SDA
SCL
START
SCL from
SCL from
Addr MSB
Master A
Master B
SCL bus
1
Line
2
SLA+R/W
Addr LSB
7
R/W
8
TA
Counting Low Period
low
Masters Start
ACK
TB
9
low
Data MSB
1
TA
2
Counting High Period
Data Byte
high
Masters Start
TB
high
7
Data LSB
ATmega16A
8
ACK
9
STOP
179

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