DS2482S-800(2009) View Datasheet(PDF) - Maxim Integrated

Part Name

Description

Manufacturer

DS2482S-800
(Rev.:2009)

Eight-Channel 1-Wire Master

Maxim Integrated 

DS2482-800: Eight-Channel 1-Wire Master

Strong Pullup (SPU)

The SPU bit controls whether the DS2482 applies a low-impedance pullup to VCC on the 1-Wire line after the last

bit of either a 1-Wire Write Byte command or after a 1-Wire Single Bit command has completed. The strong

pullup feature is commonly used with 1-Wire EEPROM devices when copying scratchpad data to the main memory

or when performing a SHA-1 computation, and with parasitically powered temperature sensors or A-to-D

converters. The respective device data sheets specify the location in the communications protocol after which the

strong pullup should be applied. The SPU bit in the configuration register of the DS2482 must be set immediately

prior to issuing the command that puts the 1-Wire device into the state where it needs the extra power.

If SPU is 1, the DS2482 applies active pullup to the rising edge of the time slot in which the strong pullup starts,

regardless of the APU bit setting. However, in contrast to setting APU = 1 for active pullup, the low-impedance

pullup will not end after tAPUOT is expired. Instead, as shown in Figure 3, the low-impedance pullup remains active

until: a) the next 1-Wire communication command (the typical case), b) by writing to the Configuration Register with

the SPU bit being 0 (alternative), or c) by issuing the Device Reset command. Additionally, when the pullup ends,

the SPU bit is automatically reset to 0. Using the strong pullup does not change the state of the APU bit in the

Configuration Register.

Figure 3. Low-Impedance Pullup Timing

Last bit of 1-Wire Write Byte or 1-Wire Single Bit Function

Vcc

Write 1

Edges with

active pull-up

Write 0

0V

tSLOT

Next

Time

Slot

Pull-up

DS2482 Pull-down

DS2482 Low Impedance Pull-up

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