ATTINY20-EK1 Atmel, ATTINY20-EK1 Datasheet - Page 142

• Manufacturer Part Number: ATTINY20-EK1
• Description: KIT EVAL TOUCH ATTINY20
• Manufacturer: Atmel

Specifications of ATTINY20-EK1

• Sensor Type: *
• Sensing Range: *
• Interface: *
• Sensitivity: *
• Voltage - Supply: *
• Embedded: *
• Utilized Ic / Part: *
• Silicon Manufacturer: Atmel
• Core Architecture: AVR
• Core Sub-architecture: TinyAVR
• Kit Contents: Board
• Svhc: No SVHC (15-Dec-2010)
• Mcu Supported Families: ATtiny20
• Tool / Board Applications: Microcontroller
• Rohs Compliant: Yes
• Tool Type: Development Kit
• Cpu Core: AVR 8
• Data Bus Width: 8 bit
• Processor To Be Evaluated: ATtiny20
• Interface Type: Touch
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Figure 17-6. Master Read Transaction
Given that the slave acknowledges the address, the master can start receiving data from the
slave. There are no limitations to the number of data packets that can be transferred. The slave
transmits the data while the master signals ACK or NACK after each data byte. The master ter-
minates the transfer with a NACK before issuing a STOP condition.
Figure 17-7
illustrates a combined transaction. A combined transaction consists of several read
and write transactions separated by a Repeated START conditions (Sr).
Figure 17-7. Combined Transaction
17.3.7
Clock and Clock Stretching
All devices connected to the bus are allowed to stretch the low period of the clock to slow down
the overall clock frequency or to insert wait states while processing data. A device that needs to
stretch the clock can do this by holding/forcing the SCL line low after it detects a low level on the
line.
Three types of clock stretching can be defined as shown in
Figure
17-8.
Figure 17-8. Clock Stretching
If the device is in a sleep mode and a START condition is detected the clock is stretched during
the wake-up period for the device.
A slave device can slow down the bus frequency by stretching the clock periodically on a bit
level. This allows the slave to run at a lower system clock frequency. However, the overall per-
formance of the bus will be reduced accordingly. Both the master and slave device can
randomly stretch the clock on a byte level basis before and after the ACK/NACK bit. This pro-
vides time to process incoming or prepare outgoing data, or performing other time critical tasks.
ATtiny20
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8235B–AVR–04/11