Datasheet

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SBAS323G − JUNE 2004 − REVISED OCTOBER 2007
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74
Port 3 (P3)
7 6 5 4 3 2 1 0 Reset Value
SFR B0h
P3.7
RD
P3.6
WR
P3.5
T1
P3.4
T0
P3.3
INT1
P3.2
INT0
P3.1
TXD0
P3.0
RXD0
FFh
P3.7−0 General-Purpose I/O Port 3. This register functions as a general-purpose I/O port. In addition, all the pins have an
bits 7−0 alternative function listed below. Each of the functions is controlled by several other SFRs. The associated Port 3
latch bit must contain a logic ‘1’ before the pin can be used in its alternate function capacity.
RD
External Data Memory Read Strobe. This pin provides an active low read strobe to an external memory device.
bit 7 If Port 0 or Port 2 is selected for external memory in the HCR1 register, this function will be enabled even if a ‘1’ is
not written to this latch bit. When external memory is selected, the settings of P3DRRH are ignored.
WR External Data Memory Write Strobe. This pin provides an active low write strobe to an external memory device.
bit 6 If Port 0 or Port 2 is selected for external memory in the HCR1 register, this function will be enabled even if a ‘1’ is
not written to this latch bit. When external memory is selected, the settings of P3DRRH are ignored.
T1 Timer/Counter 1 External Input. A 1 to 0 transition on this pin will increment Timer 1.
bit 5
T0 Timer/Counter 0 External Input. A 1 to 0 transition on this pin will increment Timer 0.
bit 4
INT1
External Interrupt 1. A falling edge/low level on this pin will cause an external interrupt 1 if enabled.
bit 3
INT0
External Interrupt 0. A falling edge/low level on this pin will cause an external interrupt 0 if enabled.
bit 2
TXD0 Serial Port 0 Transmit. This pin transmits the serial Port 0 data in serial port modes 1, 2, 3, and emits the
bit 1 synchronizing clock in serial port mode 0.
RXD0 Serial Port 0 Receive. This pin receives the serial Port 0 data in serial port modes 1, 2, 3, and is a bidirectional data
bit 0 transfer pin in serial port mode 0.