DS2411 Maxim, DS2411 Datasheet - Page 4

• Manufacturer Part Number: DS2411
• Description: The DS2411 silicon serial number is a low-cost, electronic registration number with external power supply
• Manufacturer: Maxim

Note 9:
Note 10:
Note 11:
Note 12:
Note 13:
OPERATION
The DS2411’s registration number is accessed through a single data line. The 48-bit serial number, 8-bit
family code, and 8-bit CRC are retrieved using the Maxim 1-Wire protocol. This protocol defines bus
transactions in terms of the bus state during specified time slots that are bus-master-generated falling
edges on the I/O pin. All data is read and written least significant bit first. The device requires a delay
between V
may issue presence-detect pulses.
1-Wire BUS SYSTEM
The 1-Wire bus has a single bus master and one or more slaves. In all instances, the DS2411 is a slave
device. The bus master is typically a microcontroller. The discussion of this bus system is broken down
into three topics: hardware configuration, transaction sequence, and 1-Wire signaling (signal type and
timing).
Hardware Configuration
The 1-Wire bus has a single data line, I/O. It is important that each device on the bus be able to drive I/O
at the appropriate time. To facilitate this, each device has an open-drain or three-state output. The
DS2411 has an open-drain output with an internal circuit equivalent to that shown in Figure 3. The bus
master can have the same equivalent circuit. If a bidirectional pin is not available on the master, separate
output and input pins can be connected together. The bus requires a pullup resistor at the master end of
the bus, as shown in Figure 4. A multidrop bus consists of a 1-Wire bus with multiple slaves attached.
The 1-Wire bus has a maximum data rate of 15.4kbps in standard speed and 125kbps in overdrive.
The idle state for the 1-Wire bus is high. If a transaction needs to be suspended for any reason, I/O must
remain high if the transaction is to be resumed. If the bus is pulled low, slave devices on the bus will
interpret the low as either a timeslot, or a reset depending on the duration.
Figure 1. DS2411 REGISTRATION NUMBER
MSB
MSB
8-BIT CRC CODE
CC
power-up and initial 1-Wire communication, t
The earliest recognition of a negative edge is possible at t
on the previous edge.
Interval during the negative edge on I/O at the beginning of a presence-detect pulse
between the time at which the voltage is 90% of V
10% of V
ε in Figure 7 represents the time required for the pullup circuitry to pull the voltage on I/O
up V
+ t
δ in Figure 7 represents the time required for the pullup circuitry to pull the voltage on I/O
up from V
for the master to pull the line low is t
Interval begins when the voltage drops below V
when the voltage rises above V
F
- ε and t
IL
to V
PUP
IL
LSB
TH
W0LMAX
.
to the input-high threshold of the bus master. The actual maximum duration
. The actual maximum duration for the master to pull the line low is t
MSB
+ t
F
- ε, respectively.
48-BIT SERIAL NUMBER
TH
during a positive edge on I/O.
4 of 12
RLMAX
+ t
F
PWRP
.
TL
PUP
during a negative edge on I/O and ends
(1200µs). During this time the device
LSB MSB
and the time at which the voltage is
REH
8-BIT FAMILY CODE
after V
(01h)
TH
has been reached
LSB
LSB
W1LMAX