Rainbow-electronics AT90LS4433 Manual do Utilizador descarregar pdf (Página 72)

AT90S/LS4433

1042G–AVR–09/02

I/O Ports All AVR ports have true Read-Modify-Write functionality when used as general digital

I/O ports. This means that the direction of one port pin can be changed without uninten-

tionally changing the direction of any other pin with the SBI and CBI instructions. The

same applies for changing drive value (if configured as output) or enabling/disabling of

pull-up resistors (if configured as input).

Port B Port B is a 6-bit bi-directional I/O port.

Three I/O memory address locations are allocated for the Port B, one each for the Data

B Input Pins – PINB, $16($36). The Port B Input Pins address is read only, while the

Data Register and the Data Direction Register are read/write.

All port pins have individually selectable pull-up resistors. The Port B output buffers can

sink 20 mA and thus drive LED displays directly. When pins PB0 to PB7 are used as

inputs and are externally pulled low, they will source current if the internal pull-up resis-

tors are activated.

The Port B pins with alternate functions are shown in Table 23.

When the pins are used for the alternate function, the DDRB and PORTB Registers

have to be set according to the alternate function description.

Port B Data Register – PORTB

Port B Data Direction Register

– DDRB

Port B Input Pins Address –

PINB

Table 23. Port B Pin Alternate Functions

Port Pin Alternate Functions

PB0 ICP (Timer/Counter1 Input Capture Pin)

PB1 OC1 (Timer/Counter1 Output Compare Match Output)

PB2 SS

(SPI Slave Select Input)

PB3 MOSI (SPI Bus Master Output/Slave Input)

PB4 MISO (SPI Bus Master Input/Slave Output)

PB5 SCK (SPI Bus Serial Clock)

Bit 76543210

$18 ($38)

––PORTB5 PORTB4 PORTB3 PORTB2 PORTB1 PORTB0 PORTB

Read/Write R R R/W R/W R/W R/W R/W R/W

InitialValue00000000

Bit 76543210

$17 ($37) ––DDB5 DDB4 DDB3 DDB2 DDB1 DDB0 DDRB

Read/Write R R R/W R/W R/W R/W R/W R/W

InitialValue00000000

Bit 76543210

$16 ($36) ––PINB5 PINB4 PINB3 PINB2 PINB1 PINB0 PINB

Read/Write R R R RRRRR

Initial Value 0 0 N/A N/A N/A N/A N/A N/A

1 2 ... 67 68 69 70 71 72 73 74 75 76 77 ... 124 125

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