Easyi3C is a leading supplier of embedded system tools that simplify the development and debugging of various communication protocols. The company offers a range of products designed to help engineers and developers use I3C/I2C , USB and MIPI, JEDEC, MCTP and other protocols more efficiently.

Testing DDR5 RCD based on Tower I3C Host Adapter (2)

1. Background introduction to DDR5 RCD I2C

In a DDR5 memory system, the RCD (Register Clock Driver) is the core control chip on the memory module (RDIMM). Its I2C/I3C interface (usually called the Control Bus ) is mainly used for configuring registers, monitoring status, and reading SPD information.

In the DDR5 standard, although the physical layer supports the faster I3C protocol, read and write features in I2C mode remain fundamental for backward compatibility.

The following is a summary of the core features of the DDR5 RCD read/write protocol in I2C mode:

a) Communication Fundamentals and Addressing

The control bus of DDR5 RCD follows the standard slave communication logic, but introduces a more stringent address division.

• Device Address (Slave Address): Typical RCD addressing is usually determined by fixed hardware pins (such as SA0, SA1). In a DDR5 environment, the RCD typically occupies a specific 7-bit address space (e.g., 0110xxxb).

• Multi-page access mechanism (Paging): Due to the large number of internal registers in the DDR5 RCD, the protocol employs a page selection mechanism . Before reading or writing a specific register, the target page number is usually written to the "page pointer register".
  

  
  

  
  

b) Write Protocol

DDR5 RCD write operations typically use Byte Write or Block Write modes. The I2C protocol supports a relatively complex set of formats; according to the JEDEC specification, it needs to support the following formats: 

c) Read Protocol

Read operations typically employ Byte Write or Block Write patterns. Read operations are more complex than write operations because they usually involve a "pseudo-write" process to locate the address (Combined Format).

According to the JEDEC Specification, the following format needs to be supported:

d) Summary of key differences between DDR4 and DDR5 RCD I2C

Next, we will explain in detail how to use the Tower I3C Host Adapter to test the I2C of the RCD.