SPRUIV7B May 2022 – September 2023 AM620-Q1 , AM623 , AM625 , AM625-Q1 , AM625SIP
Ethernet port transmit operations can be configured to rate limit egress data for each egress priority. There is a committed information rate (CPSW_P0_PRI_CIR_REG_y, where y = 0 to 7) and an excess information rate for each priority (CPSW_P0_PRI_EIR_REG_y, where y = 0 to 7). Rate limiting is enabled for a priority when the committed information rate for the priority is non-zero. The excess information rate for a priority is enabled when the excess information rate for the priority is non-zero. The committed information rate must be non-zero if the excess information rate is configured to be non-zero. That is, there must be a configured non-zero committed information rate for there to be a configured non-zero excess information rate. Bulk traffic on other non-rate limited priorities does not impact the committed information traffic on a priority. However, bulk traffic on other non-rate limited threads does impact the excess information rates. Rate limited channels must be the highest priority channels. For example, if two rate limited channels are required then priorities 7 and 6 should be configured for committed information (and excess information if desired). The configured transfer rate includes the inter-packet gap (12 bytes) and the preamble (8 bytes). The rate in Mbits/second that each priority is configured to send is controlled by the below equation. If the excess information rate is disabled then the committed information rate only is transferred:
Priority Transfer rate [Mbit/s] = ((((Frequency in MHZ) * CPSW_P0_PRI_CIR_REG_y) / 32768) + (((Frequency in MHZ) * CPSW_P0_PRI_EIR_REG_y) / 32768))
Where the frequency is the CPPI_ICLK frequency (in MHz) and priority 0 to 7.