ATTINY25V-15ST Atmel, ATTINY25V-15ST Datasheet - Page 97

• Manufacturer Part Number: ATTINY25V-15ST
• Description: MCU AVR 2K FLASH 4MHZ 8-SOIC
• Manufacturer: Atmel
• Series: AVR® ATtinyr

Specifications of ATTINY25V-15ST

• Package / Case: 8-SOIC (3.9mm Width)
• Voltage - Supply (vcc/vdd): 1.8 V ~ 3.6 V
• Operating Temperature: -40°C ~ 85°C
• Speed: 8MHz
• Number Of I /o: 6
• Eeprom Size: 128 x 8
• Core Processor: AVR
• Program Memory Type: FLASH
• Ram Size: 128 x 8
• Program Memory Size: 2KB (2K x 8)
• Data Converters: A/D 4x10b
• Oscillator Type: Internal
• Peripherals: Brown-out Detect/Reset, POR, PWM, WDT
• Connectivity: USI
• Core Size: 8-Bit
• Processor Series: ATTINY2x
• Core: AVR8
• Data Bus Width: 8 bit
• Data Ram Size: 128 B
• Maximum Operating Temperature: + 85 C
• Mounting Style: SMD/SMT
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

16.2
16.2.1
7598H–AVR–07/09
Functional Descriptions
Three-wire Mode
This allows the counter to count the number of bits received or transmitted and generate an
interrupt when the transfer is complete. Note that when an external clock source is selected the
counter counts both clock edges. In this case the counter counts the number of edges, and not
the number of bits. The clock can be selected from three different sources: The USCK pin,
Timer/Counter0 Compare Match or from software.
The Two-wire clock control unit can generate an interrupt when a start condition is detected on
the Two-wire bus. It can also generate wait states by holding the clock pin low after a start con-
dition is detected, or after the counter overflows.
The USI Three-wire mode is compliant to the Serial Peripheral Interface (SPI) mode 0 and 1, but
does not have the slave select (SS) pin functionality. However, this feature can be implemented
in software if necessary. Pin names used by this mode are: DI, DO, and USCK.
Figure 16-2. Three-wire Mode Operation, Simplified Diagram
Figure 16-2
Slave. The two Shift Registers are interconnected in such way that after eight USCK clocks, the
data in each register are interchanged. The same clock also increments the USI’s 4-bit counter.
The Counter Overflow (interrupt) Flag, or USIOIF, can therefore be used to determine when a
transfer is completed. The clock is generated by the Master device software by toggling the
USCK pin via the PORT Register or by writing a one to the USITC bit in USICR.
SLAVE
MASTER
Bit7
Bit7
shows two USI units operating in Three-wire mode, one as Master and one as
Bit6
Bit6
Bit5
Bit5
Bit4
Bit4
Bit3
Bit3
Bit2
Bit2
Bit1
Bit1
Bit0
Bit0
PORTxn
USCK
USCK
ATtiny25/45/85
DO
DO
DI
DI
97