SNIS133E September 2003 – February 2024 LM95010
PRODUCTION DATA
All Data Bit signal transfers are started by the master. A Data Bit 0 is indicated by a "short" pulse; a Data Bit 1 is indicated by a longer pulse. The direction of the bit is relative to the master, as follows:
A master must monitor the bus as inactive before starting a Data Bit (read or Write).
A master initiates a data write by driving the bus active (low level) for the period that matches the data value (tMtr0 or tMtr1 for a write of "0" or "1", respectively). The LM95010 will detect that the SWD becomes active within a period of tSFEdet, and will start measuring the duration of that the SWD is active in order to detect the data value.
A master initiates a data read by driving the bus for a period of tMtr0. The LM95010 will detect that the SWD have become active within a period of tSFEdet. For a data read of "0", the LM95010 will not drive the SWD. For a data read of "1" the LM95010 will start within tSFEdet to drive the SWD low for a period of tSLout1. Both master and LM95010 must monitor the time at which the bus becomes inactive to identify a data read of "0" or "1".
During each Data Bit, both the master and all the LM95010s must monitor the bus (the master for Attention Request and Reset; at the LM95010s for Start Bit, Attention Request and Reset) by measuring the time SWD is active (low). If a Start Bit, Attention Requests or Reset "bit signal" is detected, the current "bit signal" is not treated as a Data Bit.
Note that the bit rate of the protocol varies depending on the data transferred. Thus, the LM95010 has a value of "0" in reserved or unused register bits for bus bandwidth efficiency.