SPRUIE9D May 2017 – May 2024 DRA74P , DRA75P , DRA76P , DRA77P
In 1-Wire (SDQ) protocol, the host first sends an initialization pulse (by pulling the line to a logic-low state) and then waits for the slave to respond with a presence pulse before enabling any communication sequence.
As for the initialization pulse, the presence pulse is a low-level pulse on the line initiated by the slave. The timing diagram in Figure 26-31 shows the 1-Wire (SDQ) reset sequence.
Figure 26-31 1-Wire (SDQ) Reset Timing DiagramThe host drives the line to a logic-low state for a minimum of reset low time. Once the slave detects this pulse, it must drive the line to a logic-low state within the presence pulse high delay for a minimum period of presence pulse low time.
If the slave does not respond within this interval of time, a time-out event occurs and no transaction can be initiated. The host must initiate the reset sequence again before sending any command to the slave.
On the other hand, if the slave sends back its presence pulse within the specified time interval, the communication can be enabled after the reset high time.