37.4.1.2 General Call Addressing Support
The I2C Specification reserves the address 0x00 as the General Call address.
The General Call address is used to address all client modules connected to the bus at
the same time. When a host issues a General Call, all client devices may, in theory,
respond with an ACK. The General Call Enable (GCEN) bit determines whether client hardware will respond to a General Call address. When
GCEN is set (GCEN =
1
), client hardware will respond to a General Call
with an ACK, and when GCEN is clear (GCEN =
0
), the General Call is ignored, and the client responds with a NACK. When the module receives a General Call, the ADRIF bit is set and the address is stored in I2CxADB0. If
the ADRIE bit is set, the module will generate an interrupt and
stretch the clock after the 8th falling edge of SCL. This allows the client to determine
the acknowledgement response to return to the host (see the figure below).
Important: When using the General
Call addressing feature, loading the I2CxADR0/1/2/3 registers with the 0x00 address is
not recommended. Additionally, client hardware only supports General Call addressing in
7-bit Addressing modes.