DS18S20-SL+T&R Maxim Integrated Products, DS18S20-SL+T&R Datasheet - Page 11

• Manufacturer Part Number: DS18S20-SL+T&R
• Description: Board Mount Temperature Sensors Prgmble Resolution 1-Wire Parasite Pwr
• Manufacturer: Maxim Integrated Products

Specifications of DS18S20-SL+T&R

• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

SKIP ROM [CCh]
The master can use this command to address all devices on the bus simultaneously without sending out
any ROM code information. For example, the master can make all DS18S20s on the bus perform
simultaneous temperature conversions by issuing a Skip ROM command followed by a Convert T [44h]
command.
Note that the Read Scratchpad [BEh] command can follow the Skip ROM command only if there is a
single slave device on the bus. In this case, time is saved by allowing the master to read from the slave
without sending the device’s 64-bit ROM code. A Skip ROM command followed by a Read Scratchpad
command will cause a data collision on the bus if there is more than one slave since multiple devices will
attempt to transmit data simultaneously.
ALARM SEARCH [ECh]
The operation of this command is identical to the operation of the Search ROM command except that
only slaves with a set alarm flag will respond. This command allows the master device to determine if
any DS18S20s experienced an alarm condition during the most recent temperature conversion. After
every Alarm Search cycle (i.e., Alarm Search command followed by data exchange), the bus master must
return to Step 1 (Initialization) in the transaction sequence. See the Operation—Alarm Signaling section
for an explanation of alarm flag operation.
DS18S20 FUNCTION COMMANDS
After the bus master has used a ROM command to address the DS18S20 with which it wishes to
communicate, the master can issue one of the DS18S20 function commands. These commands allow the
master to write to and read from the DS18S20’s scratchpad memory, initiate temperature conversions and
determine the power supply mode. The DS18S20 function commands, which are described below, are
summarized in Table 2 and illustrated by the flowchart in Figure 15.
CONVERT T [44h]
This command initiates a single temperature conversion. Following the conversion, the resulting thermal
data is stored in the 2-byte temperature register in the scratchpad memory and the DS18S20 returns to its
low-power idle state. If the device is being used in parasite power mode, within 10µs (max) after this
command is issued the master must enable a strong pullup on the 1-Wire bus for the duration of the
conversion (t
external supply, the master can issue read-time slots after the Convert T command and the DS18S20 will
respond by transmitting 0 while the temperature conversion is in progress and 1 when the conversion is
done. In parasite power mode this notification technique cannot be used since the bus is pulled high by
the strong pullup during the conversion.
WRITE SCRATCHPAD [4Eh]
This command allows the master to write 2 bytes of data to the DS18S20’s scratchpad. The first byte is
written into the T
(byte 3 of the scratchpad). Data must be transmitted least significant bit first. Both bytes MUST be
written before the master issues a reset, or the data may be corrupted.
READ SCRATCHPAD [BEh]
This command allows the master to read the contents of the scratchpad. The data transfer starts with the
least significant bit of byte 0 and continues through the scratchpad until the 9th byte (byte 8 – CRC) is
read. The master may issue a reset to terminate reading at any time if only part of the scratchpad data is
needed.
CONV
) as described in the Powering the DS18S20 section. If the DS18S20 is powered by an
H
register (byte 2 of the scratchpad), and the second byte is written into the T
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L
DS18S20
register