OMO ElectronicOMO Electronic
Expand menu
Hello, Sign inMy Account
0 Cart

DS28EA00U+

P1-P3P4-P6P7-P9P10-P12P13-P15P16-P18P19-P21P22-P24P25-P27P28-P29
1-Wire Digital Thermometer with
Sequence Detect and PIO
DS28EA00
Maxim Integrated 7
MSB
8-BIT
CRC CODE
48-BIT SERIAL NUMBER
MSB MSBLSB
LSB
LSB
8-BIT FAMILY CODE
(42h)
MSBLSB
Figure 2. 64-Bit Registration Number
1ST
STAGE
2ND
STAGE
3RD
STAGE
4TH
STAGE
7TH
STAGE
8TH
STAGE
6TH
STAGE
5TH
STAGE
X
0
X
1
X
2
X
3
X
4
POLYNOMIAL = X
8
+ X
5
+ X
4
+ 1
INPUT DATA
X
5
X
6
X
7
X
8
Figure 3. 1-Wire CRC Generator
SCRATCHPAD (POWER-UP STATE)
BYTE
ADDRESS
TEMPERATURE LSB (50h)0
TEMPERATURE MSB (05h)1
TH REGISTER OR USER BYTE 1*2
TL REGISTER OR USER BYTE 2*
*POWER-UP STATE DEPENDS ON VALUE(S) STORED IN EEPROM.
3
CONFIGURATION REGISTER*4
RESERVED (FFh)5
RESERVED (0Ch)6
RESERVED (10h)
BACKUP EEPROM
N/A
N/A
TH REGISTER OR USER BYTE 1
TL REGISTER OR USER BYTE 2
CONFIGURATION REGISTER
N/A
N/A
N/A7
Figure 4. Memory Map
Memory Description
The memory map of the DS28EA00 is shown in Figure 4.
It consists of an 8-byte scratchpad and 3 bytes of back-
up EEPROM. The first 2 bytes form the Temperature
Readout register, which is updated after a temperature
conversion and is read only. The next 3 bytes are user-
writable; they contain the Temperature High (TH) and the
Temperature Low (TL) Alarm register and a Configuration
register. The remaining 3 bytes are “reserved.” They
power up with constant data and cannot be written by
the user. The TH, TL, and Configuration register data in
the scratchpad control the resolution of a temperature
conversion and decide whether a temperature is consid-
ered as “alarming.” TH, TL, and Configuration can be
copied to the EEPROM to become nonvolatile. The
scratchpad is automatically loaded with EEPROM data
when the DS28EA00 powers up.
The temperature reading is in °C using a 16-bit sign-
extended two’s complement format. Table 1 shows
examples of temperature and the corresponding data
for 12-bit resolution. With two’s complement, the sign
bit(s) is set if the value is negative. If the device is con-
figured for 12-bit resolution, all bits in the LS byte are
valid; for a reduced resolution, bit 0 (11-bit mode), bits
0 to 1 (10-bit mode), and bits 0 to 2 (9-bit mode) are
undefined.
The result of a temperature conversion is automatically
compared to the values in the alarm registers to deter-
mine whether an alarm condition exists. Alarm thresh-
olds are represented as two’s complement number.
With 8 bits available for sign and value, alarm thresh-
olds can be set in increments of 1°C. An alarm condi-
tion exists if a temperature conversion results in a value
that is either higher than or equal to the value stored
in the TH register or lower than or equal to the value
stored in the TL register. If a temperature alarm condi-
tion exists, the device responds to the Conditional
Search ROM command. The alarm condition is cleared
if a subsequent temperature conversion results in a
temperature reading within the boundaries defined by
the data in the TH and TL registers.
1-Wire Digital Thermometer with
Sequence Detect and PIO
DS28EA00
8 Maxim Integrated
ADDRRESS BIT 7 BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1 BIT 0
0h 2
3
2
2
2
1
2
0
2
-1
2
-2
2
-3
2
-4
LS BYTE
1h S S S S S 2
6
2
5
2
4
MS BYTE
TEMPERATURE
(°C)
DIGITAL OUTPUT
(BINARY)
DIGITAL OUTPUT
(HEX)
+85* 0000 0101 0101 0000 0550h
+25.0625 0000 0001 1001 0001 0191h
+10.125 0000 0000 1010 0010 00A2h
+0.5 0000 0000 0000 1000 0008h
0 0000 0000 0000 0000 0000h
-0.5 1111 1111 1111 1000 FFF8h
-10.125 1111 1111 0101 1110 FF5Eh
-25.0625 1111 1110 0110 1111 FE6Fh
-40 1111 1101 1000 0000 FD80h
Table 1. Temperature/Data Relationship
*
The power-on reset value of the Temperature Readout register is +85°C.
ADDRRESS BIT 7 BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1 BIT 0
2h S 2
6
2
5
2
4
2
3
2
2
2
1
2
0
HIGH ALARM (TH)
3h S 2
6
2
5
2
4
2
3
2
2
2
1
2
0
LOW ALARM (TL)
Register Detailed Descriptions
Temperature Readout Register Bitmap
Temperature Alarm Registers Bitmap
The functional assignments of the individual bits are
explained in the table below. Bits [4:0] and bit 7 have
no function and cannot be changed by the user. As a
factory default, the device operates in 12-bit resolution.
1-Wire Digital Thermometer with
Sequence Detect and PIO
DS28EA00
Maxim Integrated 9
ADDRRESS BIT 7 BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1 BIT 0
4h 0 R1 R0 1 1 1 1 1
BIT DESCRIPTION BIT(S) DEFINITION
R1, R0: Temperature
Converter Resolution
[6:5]
These bits control the resolution of the temperature converter. The codes are as follows:
R1 R0
0 0 9 bits
0 1 10 bits
1 0 11 bits
1 1 12 bits
DEVICE BEHAVIOR
CHAIN STATE
PIOB (EN)PIOA (DONE) CONDITIONAL READ ROM
OFF (Default) PIO (High Impedance) PIO (High Impedance) Not Recognized
ON EN Input Pullup On Recognized if EN is 0
DONE No Function Pulldown On (DONE Logic 0) Not Recognized
Table 2. Chain States
PIO Structure
Each PIO consists of an open-drain pulldown transistor
and an input path to read the pin state. The transistor is
controlled by the PIO output latch, as shown in Figure
5. The device function control unit connects the PIO
pins logically to the 1-Wire interface. PIOA has a pullup
path to internal V
DD
to facilitate the sequence-detect
function (see the
Block Diagram
) in conjunction with the
Chain command; PIOB is truly an open-drain structure.
The power-on default state of the PIO output transistors
is off; high-impedance, on-chip resistors (not shown in
Figure 5) pull the PIO pins to internal V
DD
.
Chain Function
The chain function is a feature that allows the 1-Wire
master to discover the physical sequence of devices
that are wired as a linear network (chain). This is partic-
ularly convenient for devices that are installed at equal
spacing along a long cable (e.g., to measure tempera-
tures at different locations inside a storage tower or
tank). Without chain function, the master needs a
lookup table to correlate the registration number to the
physical location.
The chain function requires two pins: an input (EN) to
enable a device to respond during the discovery and
an output (DONE) to inform the next device in the chain
that the discovery of its neighbor is done. The two gen-
eral-purpose ports of the DS28EA00 are reused for the
chain function. PIOB functions as an EN input and PIOA
generates the DONE signal, which is connected to the
EN input of the next device, as shown in the
Typical
Operating Circuit
. The EN input of the first device in the
chain needs to be hardwired to GND or logic 0 must be
applied for the duration of the sequence discovery
process. Besides the two pins, the sequence discovery
relies on the Conditional Read ROM command.
For the chain function and normal PIO operation to
coexist, the DS28EA00 distinguishes three chain states:
OFF, ON, and DONE. The transition from one chain
state to another is controlled through the Chain com-
mand. Table 2 summarizes the chain states and the
specific behavior of the PIO pins.
D Q
Q
PIO OUTPUT LATCH
CLOCK
PIO PINPIO PIN STATE
PIO OUTPUT LATCH STATE
PIO DATA
PIO CLOCK
Figure 5. PIO Simplified Logic Diagram
Configuration Register
P1-P3P4-P6P7-P9P10-P12P13-P15P16-P18P19-P21P22-P24P25-P27P28-P29

DS28EA00U+

Mfr. #:
Buy DS28EA00U+
Manufacturer:
Maxim Integrated
Description:
Board Mount Temperature Sensors 1-Wire Digital Therm w/Sequence Dtct-PIO
Lifecycle:
New from this manufacturer.
Delivery:
DHL FedEx Ups TNT EMS
Payment:
T/T Paypal Visa MoneyGram Western Union

Products related to this Datasheet