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DS89C420-MCL Datasheet(PDF) 6 Page - Maxim Integrated Products |
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DS89C420-MCL Datasheet(HTML) 6 Page - Maxim Integrated Products |
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6 / 58 page  DS89C420 6 of 58 PIN DIP PLCC TQFP NAME FUNCTION 10–17 11, 13– 19 5, 7–13 P3.0–P3.7 Port 3, I/O. Port 3 functions as both an 8-bit, bidirectional I/O port and an alternate functional interface for external interrupts, serial port 0, timer 0 and 1 inputs, and RD and WR strobes. The reset condition of port 3 is with all bits at a logic 1. In this state, a weak pullup holds the port high. This condition also serves as an input mode, since any external circuit that writes to the port overcomes the weak pullup. When software writes a 0 to any port pin, the DS89C420 activates a strong pulldown that remains on until either a 1 is written or a reset occurs. Writing a 1 after the port has been at 0 causes a strong transition driver to turn on, followed by a weaker sustaining pullup. Once the momentary strong driver turns off, the port again becomes both the output high and input state. The alternate modes of Port 3 are outlined below. 10 11 12 13 14 15 16 17 11 13 14 15 16 17 18 19 5 7 8 9 10 11 12 13 P3.0 P3.1 P3.2 P3.3 P3.4 P3.5 P3.6 P3.7 PORT ALTERNATE FUNCTION P3.0 RXD0 Serial Port 0 Receive P3.1 TXD0 Serial Port 0 Transmit P3.2 INT0 External Interrupt 0 P3.3 INT1 External Interrupt 1 P3.4 T0 Timer 0 External Input P3.5 T1 Timer 1 External Input P3.6 WR External Data Memory Write Strobe P3.7 RD External Data Memory Read Strobe 31 35 29 EA External Access. Allows selection of internal or external program memory. Connect to ground to force the DS89C420 to use an external memory-program memory. The internal RAM is still accessible as determined by register settings. Connect to VCC to use internal flash memory. |
Similar Part No. - DS89C420-MCL |
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Similar Description - DS89C420-MCL |
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