Single-Channel 1-Wire Master
PULLUP
DS2482-100 PULLDOWN
1-Wire SLAVE PULLDOWN
VCC
VIH1
VIL1
0V
RESET PULSE
RESISTIVE PULLUP
PRESENCE PULSE
APU CONTROLLED
EDGE
PRESENCE/SHORT DETECT
tRSTL
tSI
tMSP
tRSTH
tF1
Figure 4. 1-Wire Reset/Presence-Detect Cycle
1-Wire Single Bit
Command Code
87h
Command Parameter
Bit Byte
Description
Generates a single 1-Wire time slot with a bit value “V” as specified by the bit byte at the 1-Wire
line (see Table 2). A V value of 0b generates a write-zero time slot (Figure 5); a V value of 1b
generates a write-one time slot, which also functions as a read-data time slot (Figure 6). In either
case, the logic level at the 1-Wire line is tested at tMSR and SBR is updated.
Typical Use
To perform single-bit writes or reads at the 1-Wire line when single bit communication is
necessary (the exception).
Restriction
1-Wire activity must have ended before the DS2482-100 can process this command.
Error Response
Command code and bit byte are not acknowledged if 1WB = 1 at the time the command code is
received and the command is ignored.
Command Duration
tSLOT + maximum 262.5ns, counted from the falling SCL edge of the first bit (MSB) of the bit byte.
1-Wire Activity
Begins maximum 262.5ns after the falling SCL edge of the MSB of the bit byte.
Read Pointer Position
Status Register (for busy polling and data reading).
Status Bits Affected
1WB (set to 1 for tSLOT), SBR is updated at tMSR, DIR (may change its state).
Configuration Bits Affected
1WS, APU, SPU apply.
Table 2. Bit Allocation in the Bit Byte
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
V
x
x = Don’t care.
DS2482-100
Maxim Integrated
11