DS80C390 datasheet(5/58 Pages) DALLAS

5 / 58 page

DS80C390

5 of 58

110199

58-64,

2-8, 10

P1.0-P1.7

Port 1 - I/O. Port 1 can function as an 8-bit bi-directional I/O port,

the non-multiplexed A0 - A7 signals (when the MUX pin =1), and

as an alternate interface for internal resources. Setting the SP1EC

bit relocates RXD1 and TXD1 to Port 5. The reset condition of Port

1 is all bits at logic 1 via a weak pullup. The logic 1 state also

serves as an input mode, since external circuits writing to the port

can overdrive the weak pullup. When software clears any port pin

to 0, a strong pulldown is activated that remains on until either a 1

is written to the port pin or a reset occurs. Writing a 1 after the port

has been at 0 will activate a strong transition driver, followed by a

weaker sustaining pullup. Once the momentary strong driver turns

off, the port once again becomes the output (and input) high state.

Port Alternate Function

P1.0 T2 External I/O for Timer/Counter 2

P1.1 T2EX Timer/Counter 2 Capture/Reload Trigger

P1.2 RXD1 Serial Port 1 Input

P1.3 TXD1 Serial Port 1 Output

P1.4 INT2 External Interrupt 2 (Pos. Edge Detect)

P1.5 INT3 External Interrupt 3 (Neg. Edge Detect)

P1.6 INT4 External Interrupt 4 (Pos. Edge Detect)

P1.7 INT5 External Interrupt 5 (Neg. Edge Detect)

A8 (P2.0)

A9 (P2.1)

A10 (P2.2)

A11 (P2.3)

A12 (P2.4)

A13 (P2.5)

A14 (P2.6)

A15 (P2.7)

A15-A8 (Port 2) - Output. Port 2 serves as the MSB for external

addressing. The port automatically asserts the address MSB during

external ROM and RAM access. Although the Port 2 SFR exists,

the SFR value will never appear on the pins (due to memory

access).

Therefore accessing the Port 2 SFR is only useful for

MOVX A, @Ri or MOVX @Ri, A instructions, which use the Port

2 SFR as the external address MSB.

4-7,

10-13

13-16,

19-22

P3.0-P3.7

Port 3 - I/O. Port 3 functions as an 8-bit bi-directional I/O port,

and as an alternate interface for several resources found on the

traditional 8051. The reset condition of Port 1 is all bits at logic 1

via a weak pullup. The logic 1 state also serves as an input mode,

since external circuits writing to the port can overdrive the weak

pullup. When software clears any port pin to 0, the device activates

a strong pulldown that remains on until either a 1 is written to the

port pin or a reset occurs. Writing a 1 after the port has been at 0

will activate a strong transition driver, followed by a weaker

sustaining pullup. Once the momentary strong driver turns off, the

port once again becomes the output (and input) high state.

Port

Alternate Function

P3.0

RXD0 Serial Port 0 Input

P3.1

TXD0 Serial Port 0 Output

P3.2

INT0

External Interrupt 0

P3.3

INT1

External Interrupt 1

P3.4

T0 Timer 0 External Input

P3.5

T1/XCLK Timer 1 External Input/External Clock Output

P3.6

External Data Memory Write Strobe

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