Single-sided programmable Flash-based microcontroller in the system, 89Sxx series development board
Introduction
I designed this single-sided development board to use MCS-51 microcontroller learning tools to facilitate the development of single-chip projects. 89Sxx development board features:
DIL-based design of the 89Sxx 40, 89S51/52/53
In System Programming (ISP), through a 6-pin connector
RS-232 and RS-485 serial ports (shared pins) communicate with devices such as PC serial devices
HD44780 compatible alphanumeric LCD backlight control connection
The motherboard integrates 4 tact switches
16 general purpose IO port pins 5x2 headers (PORT0 and PORT2)
24CXX I2C EEPROM
Serial Real Time Clock (RTC) Backup Battery for the DS1302
Power rectification and voltage regulator on the board
Single-sided PCB design
Hardware
The hardware block diagram is shown in Figure 1. The MCU is a 89Sxx microcontroller. And the complete hardware schematic is shown in Figure 2.
P1 port as data bus is used for liquid crystal display (4-bit interface, printed circuit board layout is designed with 16X2 characters with backlight), on-board tact switch and connection in system programming (ISP)
PORT0 and general purpose IO port 2 for connecting external devices. PORT0 is connected to DIP switch, P0.0 and P0.1 are connected to opto-isolated input
Port 3, P3.0 and P3.1 are using the serial communication UART and P3.2 is the RS-485 control direction. P3.3 and P3.4 are used as general purpose IO port pins. Another pin that communicates with serial chips, EEPROM, RTC and serial shift registers (LED array indicators)
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