Rainbow-electronics АТ89С51 User Manual download pdf

5-11

AT89C51 In-Circuit Programming

This application note illustrates the in-cir-

cuit programmability of the Atmel

AT89C51 Flash-based microcontroller.

Guidelines for the addition of in-circuit

programmability to AT89C51 applica-

tions are presented along with an appli-

cation example and the modifications to

it required to support in-circuit program-

ming. A method is then shown by which

the AT89C51 microcontroller in the

application can be reprogrammed

remotely, over a commercial telephone

line. The circuitry described in this appli-

cation note supports five volt program-

ming only, requiring the use of an

AT89C51-XX-5. The standard AT89C51

requires 12 volts for programming.

The software for this application may be

obtained by downloading from Atmel’s

BBS: (408) 436-4309.

General Considerations

Circuitry added to support AT89C51 in-

circuit programming should appear

transparent to the application when pro-

gramming is not taking place.

/VPP must be held high during pro-

gramming. In applications which do not

utilize external program memory, this pin

may be permanently strapped to V

Applications utilizing external program

memory require that this pin be held low

during normal operation.

RST must be held active during pro-

gramming. A means must be provided

for overriding the application reset cir-

cuit, which typically asserts RST only

briefly after power is applied.

PSEN

must be held low during program-

ming, but must not be driven during nor-

mal operation.

ALE/PROG

is pulsed low during pro-

gramming, but must not be driven during

normal operation.

During programming, AT89C51 I/O ports

are used for the application of mode

select, addresses and data, possibly

requiring that the controller be isolated

from the application circuitry. How this is

done is application dependent and will

be addressed here only in general

terms.

Port Used for Input

During programming, the controller must

be isolated from signals sourced by the

application circuitry. A buffer with three-

state outputs might be inserted between

the application circuitry and the control-

ler, with the buffer outputs three-stated

when programming is enabled. Alter-

nately, a multiplexer might be used to

select between signal sources, with sig-

nals applied to the controller by either

the application circuitry or the program-

mer circuitry.

Port Used for Output

No circuit changes are required if the

application circuitry can tolerate the state

changes which occur at the port during

programming. If the prior state of the

application circuitry must be maintained

during programming, a latch might be

inserted between the controller and the

application circuitry. The latch is enabled

during programming, preserving the

state of the application circuitry.

An Application Example

The AT89C51 application shown in Fig-

ure 1 is an implementation of a moving

display. This application was selected for

its simplicity and ability to show graphi-

cally the results of in-circuit reprogram-

ming. The text to be displayed is pro-

grammed into the controller as part of its

firmware, and cannot be changed with-

out reprogramming the device.

0287D-B–9/97

8-Bit

Microcontroller

with Flash

Application

Note

1 2 3 4 5 6 ... 10 11

Microcontroller 1
Application 1

Summary of Contents

Page 1 - Application

5-11AT89C51 In-Circuit ProgrammingThis application note illustrates the in-cir-cuit programmability of the AtmelAT89C51 Flash-based microcontroller.Gu

Page 2

Microcontroller5-20Figure 5. FTP Receive Mode

Page 3

Microcontroller5-21Appendix I: Intel Hex File DefinitionHexadecimal object file format (Intel hex) is produced bymost 80C51 assembler products.Each re

Page 4

Microcontroller5-12The displayed text is presented in one of two modesselected by the four-position DIP switch. In the first mode,one character at a t

Page 5

Microcontroller5-13Remote Programming Over a Commercial Telephone LineThe programmer and display application described previ-ously are connected to a

Page 6

Microcontroller5-141200 baud modem. During normal operation, the applica-tion executes its internal program while the modem andprogrammer monitor the

Page 7

Microcontroller5-15If the reset delay expires prior to the reception of a validend-of-file packet, the modem will drop the line and the pro-grammer wi

Page 8

Microcontroller5-16Figure 1. AT89C51 Moving Display Application ExampleD0D1D2D3D4D5D6A0A1WRDL1414TU2891011211254D0D1D2D3D4D5D6A0A1WRDL1414TU389101121

Page 9

Microcontroller5-17Figure 2. AT89C51 Moving Display Application Modified for In-Circuit Programming

Page 10

Microcontroller5-18Figure 3. AT89C51 Programmer

Page 11

Microcontroller5-19Figure 4. FTP Transmit Mode

Rainbow-electronics АТ89С51 User Manual

Browse online or download User Manual for Sensors Rainbow-electronics АТ89С51. Rainbow Electronics АТ89С51 User Manual

Summary of Contents

More documents for Sensors Rainbow-electronics АТ89С51

Comments to this Manuals

Rainbow-electronics АТ89С51 User Manual

Browse online or download User Manual for Sensors Rainbow-electronics АТ89С51. Rainbow Electronics АТ89С51 User Manual

Summary of Contents

More documents for Sensors Rainbow-electronics АТ89С51

Comments to this Manuals

Related products and manuals for Sensors Rainbow-electronics АТ89С51