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8051 microcontroller to UART serial interface evaluation board

Posted: 25 Nov 2004     Print Version  Bookmark and Share

Keywords:UART 

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AN10319

8051 microcontroller to UART serial interface evaluation

board

Rev. 01 -- 26 August 2004 Application note

Document information

Info Content

Keywords 8051 microcontroller to UART, UART evaluation board, UART serial interface

Abstract The operation and description of the 8051 microcontroller to UART serial

interface is discussed in this application note. In addition, information for

obtaining the source code in C language, containing communication routines

between the 8051 core microcontroller and the UART is provided.

9397 750 13533 ) Koninklijke Philips Electronics N.V. 2004. All rights reserved.

Application note Rev. 01 -- 26 August 2004 2 of 8

Philips Semiconductors AN10319

8051 microcontroller to UART serial interface evaluation board

Contact information

For additional information, please visit: http://www.semiconductors.philips.com

For sales office addresses, please send an email to: sales.addresses@www.semiconductors.philips.com

Revision history

Rev Date Description

1 20040826 Application note; initial version (9397 750 13533).

9397 750 13533 ) Koninklijke Philips Electronics N.V. 2004. All rights reserved.

Application note Rev. 01 -- 26 August 2004 3 of 8

Philips Semiconductors AN10319

8051 microcontroller to UART serial interface evaluation board

1. Introduction

The UART Serial Evaluation kit is a useful development tool. It comes with a demo board,

firmware source code, and complete documents. The kit enables users quickly to

understand the implementation of a microcontroller such as 8051 to UART serial interface

and the UART to RS-232 serial port interface.

The description of the block diagram, hardware, software, and firmware are described in

Section 2. The source code in C language is provided to show how to write a

communication program between the 8051 microcontroller and the UART. The goal is to

help users to shorten their product development cycle.

2. Block diagram

The block diagram depicted in Figure 1 shows the bus interface between a UART and a

microcontroller such as 8051. The 8051 microcontroller sends data to and receives data

from the UART through the 8-bit parallel data bus. Then, the UART converts the parallel

data to serial data and transmits the serial data to the serial port through the RS-232 line

drivers which function is to convert the CMOS logic to TTL logic. Also, the UART receives

the serial data from the serial port through the RS-232 line receivers and converts the

serial data to an 8-bit parallel data. Then, the UART sends the parallel data to the

microcontroller.

Fig 1. Block diagram of the evaluation board

UART

002aaa888

8-bit parallel data

RS-232

DRIVERS/

RECEIVERS

transmit

receive

RTS

CTS

serial communication

SERIAL

PORT 2

address, read, write,

reset, enable

interrupt

microcontroller

P89LV51RD2

RS-232

DRIVERS/

RECEIVERS

SERIAL

PORT 1

in-system programming

9397 750 13533 ) Koninklijke Philips Electronics N.V. 2004. All rights reserved.

Application note Rev. 01 -- 26 August 2004 4 of 8

Philips Semiconductors AN10319

8051 microcontroller to UART serial interface evaluation board

3. Hardware description

The evaluation board consists of three major parts and provides a function to convert the

parallel data bus to RS232 serial port and vice versa. Also, it provides an in-system

programming function.

The functions of the three major parts are described as follows:

7 Philips P89LV51RD2 is an 8051 microcontroller. The microcontroller connection to the

UART is through the 8-bit parallel data bus and control signals - address, write, read,

reset, and chip select signals. The microcontroller acts as a host controlling the UART

device on the board with the embedded firmware.

7 Philips SC16Cxxx is a UART device interfacing between the microcontroller and

RS-232. The UART mainly consists of two sections: transmitter and receiver. The

transmitter performs parallel-to-serial conversion on data transmitted from the

microcontroller. The receiver performs serial-to-parallel conversion on data received

from a peripheral device.

7 Philips RS-232 drivers/receivers are the transceivers. The first one allows the

microcontroller to be in-system programmed through a PC's serial port such as

COM1. The second one allows the UART to be in serial communication with a

peripheral device through another PC's serial port such as COM2. The RS-232 mainly

consists of two sections: drivers (transmitters) and receivers. The drivers convert the

CMOS-logic output levels to RS-232 signals, whereas the receivers convert the

RS-232 signals to CMOS-logic output levels.

4. Software description

The programming of the demo board can be done by writing firmware code requires the

following software.

7 Raisonance is one of the embedded system vendors that provide the development

tools for the 8051 microcontroller. The software compiles the firmware code and

generates an 'Intel Hex' file. The Raisonance free evaluation development kit can be

downloaded from http://www.raisonance.com.

7 Flash Magic is a free Windows application software that allows easy programming of

Philips Flash Microcontrollers. The software loads the 'Intel Hex' file to the

microcontroller by using its in-system programming mode communicating through

serial port. The software can be downloaded from

http://www.esacademy.com/software/flashmagic.

5. In-system programming mode

Philips P89LV51RD2 microcontroller has an on-chip Flash program memory with ISP

(In-System Programming), which allows the microcontroller to be programmed without

removing the microcontroller from the board and also the microcontroller, which previously

programmed can be reprogrammed without removal from the board.

The microcontroller must be powered up in a special 'ISP mode' to perform the ISP

operation. The ISP mode allows the microcontroller to communicate with a host device

such as PC through a serial port. The host sends commands and data to the

9397 750 13533 ) Koninklijke Philips Electronics N.V. 2004. All rights reserved.

Application note Rev. 01 -- 26 August 2004 5 of 8

Philips Semiconductors AN10319

8051 microcontroller to UART serial interface evaluation board

microcontroller. The commands can be erase, read, and write. After the completion of the

ISP operation, the microcontroller is reconfigured and has to be reset or power cycled so

the microcontroller will operate normally.

The ISP programming for the device can be done using a Windows application software,

which uses an Intel Hex file as input to program it. For more information about the

software, please refer to Section 4 "Software description".

6. Firmware description

The firmware code for the evaluation board is written in C language. It can be compiled by

using an embedded C compiler. For more information about the compiler, please refer to

Section 4 "Software description".

The firmware code consists of three major blocks: Main Loop, Interrupt Service Routine,

and UART layer. Each are described below.

6.1 Main Loop

The function of the Main Loop is to reset and initialize the UART by writing a character (an

8-bit data) to the UART register. Inside the Main Loop, the microcontroller can select one

of the two methods for communicating to the UART. The two methods are polling the

UART regularly and using an interrupt handler in the interrupt service routine. If using the

interrupt handler, the microcontroller and the UART interrupt bits must be enabled. The

other function is to keep checking the event flags and pass to the appropriate subroutine

for further processing.

6.2 Interrupt Service Routine (ISR)

The microcontroller uses the interrupt service routine to handle an interrupt generated by

the UART. As soon as the UART generates an interrupt, the ISR checks the interrupt

status of the UART to determine the interrupt type and sets up proper event flags to inform

the Main Loop program for processing the interrupt.

6.3 UART layer

The UART layer handles the bus interface between the microcontroller and the UART. The

three functions in the UART layer are:

UART_Reset -- The microcontroller resets the UART device.

UART_Read -- The UART places a character on the data bus for the microcontroller to

read and the microcontroller stores the character.

UART_Write -- The microcontroller places a character on the data bus for the UART to

read.

9397 750 13533 ) Koninklijke Philips Electronics N.V. 2004. All rights reserved.

Application note Rev. 01 -- 26 August 2004 6 of 8

Philips Semiconductors AN10319

8051 microcontroller to UART serial interface evaluation board

7. Conclusion

The use of the evaluation kit allows the user to understand how the Philips UART is

interfacing with a microcontroller such as 8051. The board shows the circuit connection

between the microcontroller to the UART and the UART to RS-232 transceivers. The

source codes Mainloop.c, UART.C, and UART.H show the communication protocol

between the microcontroller and the UART. They can be accessed at

http://www.standardproducts.philips.com/support/datacom/.

Philips Semiconductors AN10319

8051 microcontroller to UART serial interface evaluation board

9397 750 13533 ) Koninklijke Philips Electronics N.V. 2004. All rights reserved.

Application note Rev. 01 -- 26 August 2004 7 of 8

8. Disclaimers

Life support -- These products are not designed for use in life support

appliances, devices, or systems where malfunction of these products can

reasonably be expected to result in personal injury. Philips Semiconductors

customers using or selling these products for use in such applications do so

at their own risk and agree to fully indemnify Philips Semiconductors for any

damages resulting from such application.

Right to make changes -- Philips Semiconductors reserves the right to

make changes in the products - including circuits, standard cells, and/or

software - described or contained herein in order to improve design and/or

performance. When the product is in full production (status `Production'),

relevant changes will be communicated via a Customer Product/Process

Change Notification (CPCN). Philips Semiconductors assumes no

responsibility or liability for the use of any of these products, conveys no

license or title under any patent, copyright, or mask work right to these

products, and makes no representations or warranties that these products are

free from patent, copyright, or mask work right infringement, unless otherwise

specified.

) Koninklijke Philips Electronics N.V. 2004

All rights are reserved. Reproduction in whole or in part is prohibited without the prior

written consent of the copyright owner. The information presented in this document does

not form part of any quotation or contract, is believed to be accurate and reliable and may

be changed without notice. No liability will be accepted by the publisher for any

consequence of its use. Publication thereof does not convey nor imply any license under

patent- or other industrial or intellectual property rights.

Date of release: 26 August 2004

Document order number: 9397 750 13533

Published in the U.S.A.

Philips Semiconductors AN10319

8051 microcontroller to UART serial interface evaluation board

9. Contents

1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

2 Block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . 3

3 Hardware description . . . . . . . . . . . . . . . . . . . . 4

4 Software description . . . . . . . . . . . . . . . . . . . . . 4

5 In-system programming mode . . . . . . . . . . . . . 4

6 Firmware description . . . . . . . . . . . . . . . . . . . . 5

6.1 Main Loop. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

6.2 Interrupt Service Routine (ISR) . . . . . . . . . . . . 5

6.3 UART layer . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

7 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

8 Disclaimers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7





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