Holtek HT-IDE, Руководство пользователя

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Input/Output ports system calls
The Holtek C language provides the following system calls for accessing the
input/output ports. These system calls are implemented without ’call’ in-
structions to reduce the number of stacks used.
→
Input/Output ports
•
unsigned char peekPX()
Read data from port X, X=A,B,C,D,E,F,G
–
Example
unsigned char i;
i= peekPA(); //read input value from the port A, saved in i
•
void pokePX (unsigned char)
Write data to port X, X=A,B,C,D,E,F,G
–
Example
pokePC (0
×
00); //write a char 0
×
00 to the port C
→
Read/Write control registers
•
unsigned char peekPXC()
Read data from port X control register, X= A,B,C,D,E,F,G
–
Example
unsigned char i;
i= peekPEC(); //read an input value from the control register
//of port E, saved in i
•
void pokePXC (unsigned char)
write data to port X control register, X=A,B,C,D,E,F,G
–
Example
pokePBC(0
×
20); //write a value of 0x20 to the control
//register of port B
→
Set/Clear bits of ports
•
void setPX()
set port X, X=A,B,C,D,E,F,G
–
Example
setPD(); //set port D
•
void setPXi()
set bit i of port X, i=0,1,2,3,4,5,6,7 and X=A,B,C,D,E,F,G
–
Example
setPD3(); //set bit 3 of port D
•
void clrPX()
clear port X,X=A,B,C,D,E,F,G
– Example
clrPC(); //clear port C
Chapter 9 Holtek C Language
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