Tools

8051 Tools

This is a collection of code generators for 8051-based chips from Microchip and STC.

8051 Code Generators

Port Configuration
External IRQ
UART Baudrate
Timer Delay Tool

Check out detailed specifications here. Note that is only works for modern MCUs, classic 8051 chips and classic-like derivatives like the AT89C5x and STC89C5x series only support quasi-bidirectional modes and lack the port mode registers PxMx

Port:	Quasi-Bidirectional	Push-Pull	Input	Open-Drain
P0.0	Quasi-Bidirectional	Push-Pull	Input-Only	Open-Drain
P0.1	Quasi-Bidirectional	Push-Pull	Input-Only	Open-Drain
P0.2	Quasi-Bidirectional	Push-Pull	Input-Only	Open-Drain
P0.3	Quasi-Bidirectional	Push-Pull	Input-Only	Open-Drain
P0.4	Quasi-Bidirectional	Push-Pull	Input-Only	Open-Drain
P0.5	Quasi-Bidirectional	Push-Pull	Input-Only	Open-Drain
P0.6	Quasi-Bidirectional	Push-Pull	Input-Only	Open-Drain
P0.7	Quasi-Bidirectional	Push-Pull	Input-Only	Open-Drain

Generated code for SDCC (note Keil does not like bitfields)

	/* Port Mode Configuration */
	P0M0 = 0b00000000;
	P0M1 = 0b00000000;
	/*       |||||||+--- P0.0 = Quasi-Bidirectional */
	/*       ||||||+---- P0.1 = Quasi-Bidirectional */
	/*       |||||+----- P0.2 = Quasi-Bidirectional */
	/*       ||||+------ P0.3 = Quasi-Bidirectional */
	/*       |||+------- P0.4 = Quasi-Bidirectional */
	/*       ||+-------- P0.5 = Quasi-Bidirectional */
	/*       |+--------- P0.6 = Quasi-Bidirectional */
	/*       +---------- P0.7 = Quasi-Bidirectional */

Verbose Mode

Check out detailed specifications here. Note that classic MCS-51 derivatives like the AT89C5x only have two external interrupt (INT0, INT1) sources. The STC89/STC90 series extends this for up to four sources (INT0 to INT3) depending on the model, but that is not portable to other STC chips that have specific flag registers in different places.

Source	Type
Enable INT0
Enable INT1
Enable INT2
Enable INT3

Generated code for SDCC (note Keil has different IRQ shims)

#include <8051.h>


void ext_init(void) {
}

Verbose Mode

Check out detailed specifications here. Note that classic MCS-51 derivatives like the AT89C5x can use Timer 1 as variable baud rate generator for the UART, but 8052 derivatives like the STC89C52 also support Timer 2 as baud rate generator.

Frequency......: UART Bits..:
Target Baudrate: Timer......:
Double Rate (SMOD) Est. Baudrate..: 9600 Est. Error.: 0.00 %

Generated code for SDCC (note Keil does not like bitfields)

void uart1_init(void) {
	PCON &= 0x7F;	/* SMOD - Baud rate not doubled */
	SCON = 0x50;	/* 8 bits and variable baudrate */
	TMOD &= 0x0F;	/* Clear timer 1 settings */
	TMOD |= 0x20;	/* Set timer 1 in auto reload mode */
	TL1 = 0xfd;	/* Initial timer value */
	TH1 = 0xfd;	/* Set reload value */
	ET1 = 0;	/* Disable Timer 1 interrupt */
	TR1 = 1;	/* Timer 1 start */
}

Verbose Mode

Check out detailed specifications here. Note that Timer 2 is only available on 8052 derivatives, and that classic MCS-51 derivatives have a 12T cycle.

Frequency......: Machine Cycle:
Interval.......: Timer........:
Actual Interval: 199.65 us Mode.........:
Error..........: 0.17 %
Generated code for SDCC (note Keil does not like bitfields)

void timer0_init(void) {
	TMOD &= 0xF0;	/* Clear Timer 0 mode bits */
	TMOD |= 0x1;	/* Set Timer 0 mode to 16-bit */
	TH0 = 0xff;	/* Set Timer 0 high byte for 16-bit mode */
	TL0 = 0x48;	/* Set Timer 0 low byte for 16-bit mode */
	TF0 = 0;	/* Clear Timer 0 overflow flag */
	TR0 = 1;	/* Start Timer 0 */
}

Verbose Mode

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