Rainbow Electronics ATtiny2313 - Manual (Page 54)

54
ATtiny2313
2543A–AVR–08/03
MCU Control Register –
MCUCR
• Bit 7 – PUD: Pull-up Disable
When this bit is written to one, the pull-ups in the I/O ports are disabled even if the DDxn
and PORTxn Registers are configured to enable the pull-ups ({DDxn, PORTxn} = 0b01).
See “Configuring the Pin” on page 48 for more details about this feature.
Alternate Functions of Port A The Port A pins with alternate functions are as shown in Table 5.
Alternate Functions of Port B The Port B pins with alternate functions are shown in Table 26.
The alternate pin configuration is as follows:
• USCK/SCL/PCINT7 - Port B, Bit 7
USCK: Three-wire mode Universal Serial Interface Clock.
SCL: Two-wire mode Serial Clock for USI Two-wire mode.
PCINT7: Pin Change Interrupt source 7. The PB7 pin can serve as an external interrupt
source.
• DO/PCINT6 - Port B, Bit 6
DO: Three-wire mode Universal Serial Interface Data output. Three-wire mode Data out-
put overrides PORTB6 value and it is driven to the port when data direction bit DDB6 is
set (one). However the PORTB6 bit still controls the pull-up enabling pull-up, if direction
is input and PORTB6 is set (one).
Bit 7 6 5 4 3 2 1 0
PUD SM1 SE SM0 ISC11 ISC10 ISC01 ISC00 MCUCR
Read/Write R/W R/W R/W R/W R/W R/W R/W R/W
Initial Value 0 0 0 0 0 0 0 0
Table 25. Port A Pins Alternate Functions
Port Pin Alternate Function
PA2 RESET, dW
PA1 XTAL2
PA0 XTAL1
Table 26. Port B Pins Alternate Functions
Port Pin Alternate Functions
PB7 USCK/SCL/PCINT7
PB6 DO/PCINT6
PB5 DI/SDA/PCINT5
PB4 OC1B/PCINT4
PB3 OC1A/PCINT3
PB2 OC0A/PCINT2
PB1 AIN1/PCINT1
PB0 AIN0/PCINT0