DS18S20

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Related Application Notes

The following Application Notes can be applied to the DS18S20. These notes can be obtained from the

Application Note 27: “Understanding and Using Cyclic Redundancy Checks with Dallas Semiconductor

Touch Memory Product”

Application Note 55: “Extending the Contact Range of Touch Memories”

Application Note 74: “Reading and Writing Touch Memories via Serial Interfaces”

Application Note 104: “Minimalist Temperature Control Demo”

Application Note 105: “High Resolution Temperature Measurement with Dallas Direct–to–Direct

Temperature Sensors”

Application Note 106: “Complex MicroLANs”

Application Note 108: “MicroLAN – In the Long Run”

Sample 1–Wire subroutines that can be used in conjunction with AN74 can be downloaded from the

website or our Anonymous FTP Site.

MEMORY FUNCTION EXAMPLE Table 3

Example: Bus Master initiates temperature conversion, then reads temperature (parasite power assumed).

MASTER MODE

DATA (LSB FIRST)

COMMENTS

TX

Reset

Reset pulse (480-960 µs).

RX

Presence

Presence pulse.

TX

55h

Issue “Match ROM” command.

TX

<64-bit ROM code>

Issue address for DS18S20.

TX

44h

Issue “ Convert T” command.

TX

<I/O LINE HIGH>

I/O line is held high for at least 750 ms by bus master to

allow conversion to complete.

TX

Reset

Reset pulse.

RX

Presence

Presence pulse.

TX

55h

Issue “Match ROM” command.

TX

<64-bit ROM code>

Issue address for DS18S20.

TX

BEh

Issue “Read Scratchpad” command.

RX

<9 data bytes>

Read entire scratchpad plus CRC; the master now

recalculates the CRC of the eight data bytes received

from the scratchpad, compares the CRC calculated and

the CRC read. If they match, the master continues; if

not, this read operation is repeated.

TX

Reset

Reset pulse.

RX

Presence

Presence pulse, done.