Datasheet

DS2482-100: Single-Channel 1-Wire Master
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Figure 1. Block Diagram
I²C
Interface
Controller
SDA
SCL
Config
Register
T-Time OSC
I/O
Controller
Status
Register
Line
XCVR
A
D0
A
D1
IO
Read Data
Register
PCTLZ
DETAILED DESCRIPTION
The DS2482-100 is a self-timed 1-Wire master, which supports advanced 1-Wire waveform features including
standard and Overdrive speeds, active pullup, strong pullup for power delivery, and presence-pulse masking. The
active pullup affects rising edges on the 1-Wire side. The strong pullup function uses the same pullup transistor as
the active pullup but with a different control algorithm. In addition, the strong pullup activates the PCTLZ pin,
controlling optional external circuitry to deliver additional power beyond the capabilities of the on-chip pullup
transistor. Once supplied with command and data, the I/O controller of the DS2482-100 performs time-critical
1-Wire communication functions such as reset/presence detect cycle, read-byte, write-byte, single-bit R/W and
triplet for ROM Search, without requiring interaction with the host processor. The host obtains feedback
(completion of a 1-Wire function, presence pulse, 1-Wire short, search direction taken) through the Status register
and data through the Read Data register. The DS2482-100 communicates with a host processor through its I
2
C
bus interface in standard mode or in fast mode. The logic state of two address pins determines the I
2
C slave
address of the DS2482-100, allowing up to four devices operating on the same bus segment without requiring a
hub.
DEVICE REGISTERS
The DS2482-100 has three registers that the I²C host can read: Configuration, Status, and Read Data. These
registers are addressed by a read pointer. The position of the read pointer, i.e., the register that the host reads in a
subsequent read access, is defined by the instruction that the DS2482-100 executed last. The host has read and
write access to the Configuration register to enable certain 1-Wire features.
Configuration Register
The DS2482-100 supports four 1-Wire features that are enabled or selected through the Configuration register.
These features are:
 Active Pullup (APU)
 Presence Pulse Masking (PPM)
 Strong Pullup (SPU)
 1-Wire Speed (1WS)
These features can be selected in any combination. While APU, PPM, and 1WS maintain their state, SPU returns
to its inactive state as soon as the strong pullup has ended.
Configuration Register Bit Assignment
bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0
1WS SPU PPM APU 1WS SPU PPM APU
After a device reset (power-up cycle or initiated by the Device Reset command) the Configuration register reads
00h. When writing to the Configuration register, the new data is accepted only if the upper nibble (bits 7 to 4) is the
one's complement of the lower nibble (bits 3 to 0). When read, the upper nibble is always 0h.
DS2482-100