Datasheet

DS2762 High-Precision Li+ Battery Monitor With Alerts
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I/O SIGNALING
The 1-Wire bus requires strict signaling protocols to ensure data integrity. The four protocols used by the DS2762
are as follows: the initialization sequence (reset pulse followed by presence pulse), write 0, write 1, and read data.
The bus master initiates all these types of signaling except the presence pulse.
The initialization sequence required to begin any communication with the DS2762 is shown in Figure 18. A
presence pulse following a reset pulse indicates that the DS2762 is ready to accept a net address command. The
bus master transmits (Tx) a reset pulse for t
RSTL
. The bus master then releases the line and goes into receive mode
(Rx). The 1-Wire bus line is then pulled high by the pullup resistor. After detecting the rising edge on the DQ pin,
the DS2762 waits for t
PDH
and then transmits the presence pulse for t
PDL
.
Figure 18. 1-Wire Initialization Sequence
WRITE-TIME SLOTS
A write-time slot is initiated when the bus master pulls the 1-Wire bus from a logic-high (inactive) level to a logic-low
level. There are two types of write-time slots: write 1 and write 0. All write-time slots must be t
SLOT
(60ms to 120ms)
in duration with a 1ms minimum recovery time, t
REC
, between cycles. The DS2762 samples the 1-Wire bus line
between 15ms and 60ms after the line falls. If the line is high when sampled, a write 1 occurs. If the line is low when
sampled, a write 0 occurs (Figure 19). For the bus master to generate a write 1 time slot, the bus line must be
pulled low and then released, allowing the line to be pulled high within 15ms after the start of the write time slot. For
the host to generate a write 0 time slot, the bus line must be pulled low and held low for the duration of the write-
time slot.
READ-TIME SLOTS
A read-time slot is initiated when the bus master pulls the 1-Wire bus line from a logic-high level to a logic-low level.
The bus master must keep the bus line low for at least 1ms and then release it to allow the DS2762 to present valid
data. The bus master can then sample the data t
RDV
(15ms) from the start of the read-time slot. By the end of the
read-time slot, the DS2762 releases the bus line and allows it to be pulled high by the external pullup resistor. All
read-time slots must be t
SLOT
(60ms to 120ms) in duration with a 1ms minimum recovery time, t
REC
, between cycles.
See Figure 19 for more information.
t
RSTL
t
PDL
t
RSTH
t
PDH
PACK+
PACK-
LINE TYPE LEGEND:
BUS MASTER
ACTIVE LOW
DS2762 ACTIVE LOW
RESISTOR PULLUP
BOTH BUS MASTER AND
DS2762 ACTIVE LOW
DQ