DS2404 Просмотр технического описания (PDF) - Dallas Semiconductor -> Maxim Integrated

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DS2404

EconoRAM Time Chip

Dallas Semiconductor -> Maxim Integrated 

DS2404

Read Memory [F0h]

The read memory command may be used to read the entire memory. After issuing the command, the user

must provide the 2-byte target address. After the two bytes, the user reads data beginning from the target

address and may continue until the end of memory, at which point logic 1’s will be read. It is important to

realize that the target address registers will contain the address provided. The ending offset/data status

byte is unaffected.

The hardware of the DS2404 provides a means to accomplish error-free writing to the memory section.

To safeguard reading data in the 1-Wire environment and to simultaneously speed up data transfers, it is

recommended to packetize data into data packets of the size of one memory page each. Such a packet

would typically store a 16-bit CRC with each page of data to ensure rapid, error-free data transfers that

eliminate having to read a page multiple times to determine if the received data is correct or not. (See the

Book of DS19xx iButton Standards, Chapter 7 for the recommended file structure to be used with the 1-

Wire environment.)

MEMORY FUNCTION EXAMPLES

Example 1: Write one page of data to page 15

Read page 15 (3-wire port)

MASTER MODE

DATA(LSB FIRST)

TX

Reset

TX

0Fh

TX

E0h

TX

01h

TX

<32 data bytes>

TX

Reset

TX

AAh

RX

E0h

RX

01h

RX

1Fh

RX

<32 data bytes>

TX

Reset

TX

55h

TX

E0h

TX

01h

TX

1Fh

RX

<busy indicator>

TX

Reset

TX

F0h

TX

E0h

TX

01h

RX

<32 data bytes>

TX

Reset

COMMENTS

Master pulses RST low

Issue “write scratchpad” command

TA1, beginning offset=0

TA2, address=01E0h

Write 1 page of data to scratchpad

Master pulses RST low

Issue “read scratchpad” command

Read TA1, beginning offset=0

Read TA2, address=01E0h

Read E/S, ending offset=31d, flags=0

Read scratchpad data and verify

Master pulses RST low

Issue “copy scratchpad” command

TA1

TA2

AUTHORIZATION CODE

E/S

Wait until DQ=0 (~30 µs typical)

Master pulses RST low

Issue “read memory” command

TA1, beginning offset=0

TA2, address=01E0h

Read memory page 15 and verify

Master pulses RST low, done

NOTE: The ROM function commands do not apply to the 3-wire port. After RST is at a high level, the

device expects to receive a memory function command.

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