C51: Creating CPU Header Files

Information in this article applies to:

• C51 All Versions

QUESTION

How do I create my own header file for a particular microcontroller?

ANSWER

Most CPU header files are already created and come with the Keil tools. For those chips without a header file, you may use the following template.

There are several keywords you must replace in this template.

• HeaderName is the name of the header file without the .H extension. This may be REG123 (for the XYZ 123 chip) or it may be XYZ123. It's really your choice.
• ChipName is the name of the manufacturer and the name of the chip. For example, Intel 80C51.

/*--------------------------------------------------------------------------
HeaderName.H

Header file for the ChipName.
Copyright (c) 2001 Keil Software, Inc.  All rights reserved.
--------------------------------------------------------------------------*/

/*------------------------------------------------
Make sure that this file gets included only once.
------------------------------------------------*/
#ifndef HeaderName_HEADER_FILE
#define HeaderName_HEADER_FILE 1

/*------------------------------------------------
Byte Registers
------------------------------------------------*/
sfr P0      = 0x80;
sfr SP      = 0x81;
sfr DPL     = 0x82;
sfr DPH     = 0x83;
sfr PCON    = 0x87;
sfr TCON    = 0x88;
sfr TMOD    = 0x89;
sfr TL0     = 0x8A;
sfr TL1     = 0x8B;
sfr TH0     = 0x8C;
sfr TH1     = 0x8D;
sfr P1      = 0x90;
sfr SCON    = 0x98;
sfr SBUF    = 0x99;
sfr P2      = 0xA0;
sfr IE      = 0xA8;
sfr P3      = 0xB0;
sfr IP      = 0xB8;
sfr PSW     = 0xD0;
sfr ACC     = 0xE0;
sfr B       = 0xF0;

/*------------------------------------------------
P0 Bit Registers
------------------------------------------------*/
sbit P0_0 = 0x80;
sbit P0_1 = 0x81;
sbit P0_2 = 0x82;
sbit P0_3 = 0x83;
sbit P0_4 = 0x84;
sbit P0_5 = 0x85;
sbit P0_6 = 0x86;
sbit P0_7 = 0x87;

/*------------------------------------------------
PCON Bit Values
------------------------------------------------*/
#define IDL_    0x01
#define STOP_   0x02

#define SMOD_   0x80

/*------------------------------------------------
TCON Bit Registers
------------------------------------------------*/
sbit IT0  = 0x88;
sbit IE0  = 0x89;
sbit IT1  = 0x8A;
sbit IE1  = 0x8B;
sbit TR0  = 0x8C;
sbit TF0  = 0x8D;
sbit TR1  = 0x8E;
sbit TF1  = 0x8F;

/*------------------------------------------------
TMOD Bit Values
------------------------------------------------*/
#define T0_M0_   0x01
#define T0_M1_   0x02
#define T0_CT_   0x04
#define T0_GATE_ 0x08
#define T1_M0_   0x10
#define T1_M1_   0x20
#define T1_CT_   0x40
#define T1_GATE_ 0x80

#define T1_MASK_ 0xF0
#define T0_MASK_ 0x0F

/*------------------------------------------------
P1 Bit Registers
------------------------------------------------*/
sbit P1_0 = 0x90;
sbit P1_1 = 0x91;
sbit P1_2 = 0x92;
sbit P1_3 = 0x93;
sbit P1_4 = 0x94;
sbit P1_5 = 0x95;
sbit P1_6 = 0x96;
sbit P1_7 = 0x97;

/*------------------------------------------------
SCON Bit Registers
------------------------------------------------*/
sbit RI   = 0x98;
sbit TI   = 0x99;
sbit RB8  = 0x9A;
sbit TB8  = 0x9B;
sbit REN  = 0x9C;
sbit SM2  = 0x9D;
sbit SM1  = 0x9E;
sbit SM0  = 0x9F;

/*------------------------------------------------
P2 Bit Registers
------------------------------------------------*/
sbit P2_0 = 0xA0;
sbit P2_1 = 0xA1;
sbit P2_2 = 0xA2;
sbit P2_3 = 0xA3;
sbit P2_4 = 0xA4;
sbit P2_5 = 0xA5;
sbit P2_6 = 0xA6;
sbit P2_7 = 0xA7;

/*------------------------------------------------
IE Bit Registers
------------------------------------------------*/
sbit EX0  = 0xA8;       /* 1=Enable External interrupt 0 */
sbit ET0  = 0xA9;       /* 1=Enable Timer 0 interrupt */
sbit EX1  = 0xAA;       /* 1=Enable External interrupt 1 */
sbit ET1  = 0xAB;       /* 1=Enable Timer 1 interrupt */
sbit ES   = 0xAC;       /* 1=Enable Serial port interrupt */

sbit EA   = 0xAF;       /* 0=Disable all interrupts */

/*------------------------------------------------
P3 Bit Registers (Mnemonics & Ports)
------------------------------------------------*/
sbit P3_0 = 0xB0;
sbit P3_1 = 0xB1;
sbit P3_2 = 0xB2;
sbit P3_3 = 0xB3;
sbit P3_4 = 0xB4;
sbit P3_5 = 0xB5;
sbit P3_6 = 0xB6;
sbit P3_7 = 0xB7;

sbit RXD  = 0xB0;       /* Serial data input */
sbit TXD  = 0xB1;       /* Serial data output */
sbit INT0 = 0xB2;       /* External interrupt 0 */
sbit INT1 = 0xB3;       /* External interrupt 1 */
sbit T0   = 0xB4;       /* Timer 0 external input */
sbit T1   = 0xB5;       /* Timer 1 external input */
sbit WR   = 0xB6;       /* External data memory write strobe */
sbit RD   = 0xB7;       /* External data memory read strobe */

/*------------------------------------------------
IP Bit Registers
------------------------------------------------*/
sbit PX0  = 0xB8;
sbit PT0  = 0xB9;
sbit PX1  = 0xBA;
sbit PT1  = 0xBB;
sbit PS   = 0xBC;
sbit PT2  = 0xBD;

/*------------------------------------------------
PSW Bit Registers
------------------------------------------------*/
sbit P    = 0xD0;

sbit OV   = 0xD2;
sbit RS0  = 0xD3;
sbit RS1  = 0xD4;
sbit F0   = 0xD5;
sbit AC   = 0xD6;
sbit CY   = 0xD7;

/*------------------------------------------------
Interrupt Vectors:
Interrupt Address = (Number * 8) + 3
------------------------------------------------*/
#define IE0_VECTOR      0  /* 0x03 External Interrupt 0 */
#define TF0_VECTOR      1  /* 0x0B Timer 0 */
#define IE1_VECTOR      2  /* 0x13 External Interrupt 1 */
#define TF1_VECTOR      3  /* 0x1B Timer 1 */
#define SIO_VECTOR      4  /* 0x23 Serial port */

/*------------------------------------------------
------------------------------------------------*/
#endif

As you can see there are several sections in the header file that you must complete:

• Byte Registers are SFRs that are located at a particular BYTE address. Examples of these are P0 (at 0x80), P1 (at 0x90), P2 (at 0xA0), and P3 (at 0xB0).
• Bit Registers are SFRs that are located at a particular BIT address. Examples of these are the pins of P1.
• Bit Values are bit values for BYTE SFRs that are not bit-addressable. Examples of these are the bits for the TMOD SFR.
• Interrupt Vectors are definitions for the interrupt vector numbers that are used when you create interrupt functions.

Most of this information is available from the databook for the device you are using.

• Typically, there is a table of the BYTE SFRs.
• The BIT SFRs are bits within the BYTE SFRs whose address ends in 0 or 8. There are BIT SFRs for BYTE SFRs at addresses 0x80, 0x88, 0x90, 0x98, 0xA0, 0xA8, and so on.
• The values of the bits for other (non-bit-addressable) SFRs may be found scattered throughout the databook.
• The values for the interrupt vectors is usually found in the databook in a chapter titled Interrupts. Refer to C51: Interrupt Vector Numbers for information on calculating the interrupt vector number from the interrupt vector address.

Once you have completed your header file, copy it into your project directory and include it in your source files.

Last Reviewed: Thursday, February 25, 2021