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Applies to: C51 C Compiler
Information in this article applies to:
How do I write to the output ports of the 8051 in C?
Before you may write to an output port, you must define the SFR(s) for port you want to write to. You may write your own SFR definitions or you may include the register definition files (header files) for your particular microcontroller.
sfr P1 = 0x90; // PORT 1 SFR sbit P1_1 = 0x91; // Port 1.1 SFR bit
#include <reg51.h> // Include register definitions for the Intel 8051
To write a byte value to Port 1 (all bits of port 1 will be set to the corresponding bits of the value written):
P1 = 0xAA;
This sets P1.0, P1.2, P1.4, and P1.6 low (0) and P1.1, P1.3, P1.5, and P1.7 high (1).
To write to a single port line:
P1_1 = 0;
This sets P1.1 low (0).
Article last edited on: 2000-06-24 00:00:00
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