Atmel C51 Datenblatt PDF herunterladen (Seite 21)

AT89S53

4-235

8. Repeat steps 3 through 7 changing the address and

data for the entire 12K-byte array or until the end of the

object file is reached.

9. Power-off sequence:

Set XTAL1 to “L”.

Set RST and EA

pins to “L”.

Tur n V

power off.

DATA Polling

The AT89S53 features DATA Polling to indicate the end of a

write cycle. During a write cycle in the parallel or serial pro-

gramming mode, an attempted read of the last byte written

will result in the complement of the written datum on P0.7

(parallel mode), and on the MSB of the serial output byte

on MISO (serial mode). Once the write cycle has been

completed, true data are valid on all outputs, and the next

cycle may begin. DATA

Polling may begin any time after a

write cycle has been initiated.

Ready/Busy

The progress of byte programming in the parallel program-

ming mode can also be monitored by the RDY/BSY

output

signal. Pin P3.4 is pulled Low after ALE goes High during

programming to indicate BUSY

. P3.4 is pulled High again

when programming is done to indicate READY.

Program Verify

If lock bits LB1 and LB2 have not been programmed, the

programmed Code can be read back via the address and

data lines for verification. The state of the lock bits can also

be verified directly in the parallel programming mode. In the

serial programming mode, the state of the lock bits can only

be verified indirectly by observing that the lock bit features

are enabled.

Chip Erase

In the parallel programming mode, chip erase is initiated by

using the proper combination of control signals and by

holding ALE/PROG

low for 10 ms. The Code array is writ-

ten with all “1”s in the Chip Erase operation.

In the serial programming mode, a chip erase operation is

initiated by issuing the Chip Erase instruction. In this mode,

chip erase is self-timed and takes about 16 ms.

During chip erase, a serial read from any address location

will return 00H at the data outputs.

Serial Programming Fuse

A programmable fuse is available to disable Serial Pro-

gramming if the user needs maximum system security. The

Serial Programming Fuse can only be programmed or

erased in the Parallel Programming Mode.

The AT89S53 is shipped with the Serial Programming

Mode enabled.

Reading the Signature Bytes:

The signature bytes are

read by the same procedure as a normal verification of

locations 030H and 031H, except that P3.6 and P3.7 must

be pulled to a logic low. The values returned are as follows:

(030H) = 1EH indicates manufactured by Atmel

(031H) = 53H indicates 89S53

Programming Interface

Every code byte in the Flash array can be written, and the

entire array can be erased, by using the appropriate combi-

nation of control signals. The write operation cycle is self-

timed and once initiated, will automatically time itself to

completion.

All major programming vendors offer worldwide support for

the Atmel microcontroller series. Please contact your local

programming vendor for the appropriate software revision.

Serial Downloading

The Code memory array can be programmed using the

serial SPI bus while RST is pulled to V

. The serial inter-

face consists of pins SCK, MOSI (input) and MISO (output).

After RST is set high, the Programming Enable instruction

needs to be executed first before program/erase operations

can be executed.

An auto-erase cycle is built into the self-timed programming

operation (in the serial mode ONLY) and there is no need

to first execute the Chip Erase instruction unless any of the

lock bits have been programmed. The Chip Erase opera-

tion turns the content of every memory location in the Code

array into FFH.

The Code memory array has an address space of 0000H to

2FFFH.

Either an external system clock is supplied at pin XTAL1 or

a crystal needs to be connected across pins XTAL1 and

XTAL2. The maximum serial clock (SCK) frequency should

be less than 1/40 of the crystal frequency. With a 24 MHz

oscillator clock, the maximum SCK frequency is 600 kHz.

1 2 ... 16 17 18 19 20 21 22 23 24 25 26 ... 33 34

Kommentare zu diesen Handbüchern

Keine Kommentare

Atmel C51 Datenblatt Seite 21

Kommentare zu diesen Handbüchern

Verwandte Produkte und Handbücher für Stromgeneratoren Atmel C51