DS2482S-800+TR MAXIM [Maxim Integrated Products], DS2482S-800+TR Datasheet - Page 7

• Manufacturer Part Number: DS2482S-800+TR
• Description: Eight-Channel 1-Wire Master
• Manufacturer: MAXIM [Maxim Integrated Products]

Strong Pullup (SPU)
The SPU bit controls whether the DS2482 applies a low-impedance pullup to V
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 t
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
V
0V
cc
APUOT
Pull-up
Write 1
Last bit of 1-Wire Write Byte or 1-Wire Single Bit Function
is expired. Instead, as shown in Figure 3, the low-impedance pullup remains active
DS2482 Pull-down
Write 0
Edges with
active pull-up
t
SLOT
7 of 23
DS2482 Low Impedance Pull-up
CC
on the 1-Wire line after the last
Next
Time
Slot