3.3 Solid State Drive (SSD) Sideband Communication
As more advanced SSDs appear in the datacenter market, the SNIA® Enterprise and Datacenter Standard Form Factor (EDSFF) has been adopted as the new SSD form factor, offering several advantages over the previous older U.2 and M.2 form factors. The EDSFF form factors use the NVMe® protocol over the PCIe® interface and dedicated connectors (SNIA SFF-TA-1002 specification). The EDSFF pinout and functions specification (SNIA SFF-TA-1009) has adopted the I3C protocol for sideband communication as a natural upgrade from the SMBus protocol. Refer to the SNIA website for SFF Specifications.
In a typical datacenter environment, the Baseboard Management Controller (BMC) uses the Management Component Transport Protocol (MCTP) to communicate with other management controllers/devices. MCTP is a media-independent protocol supporting I3C and SMBus as the underlying communication protocol. The 8-bit PIC microcontrollers with I2C and I3C modules support both MCTP-over-I3C and MCTP-over-SMBus binding specifications, allowing it to be an ideal device for system management for providing next generation I3C support while still being SMBus compatible. Refer to the DMTF® website for MCTP Transport Binding Specifications.
The 8-bit PIC microcontrollers can have up to two I3C Target modules, which allows the PIC microcontroller to connect to the onboard SSD controller for system management in addition to being connected to the BMC through EDSFF/PCIe connector for sideband communication. One such example featuring various products from the Microchip portfolio is shown in Figure 3-3.