SLVSF02D March 2019 – May 2020 TPS23881
COMMAND = 29h with 1 Data Byte, Read/Write
|LEGEND: R/W = Read/Write; R = Read only; -n = value after reset|
|7 , 3||4PWnn||R/W||0||4-Pair wired configuration bits
4PWnn = 1: Channels 3/4 or 1/2 are wired in a 4-pair configuration
4PWnn = 0: Channels 3/4 or 1/2 are wired in 2-pair configurations
|6 - 4 , 2 - 0||MCnn_2-0||R/W||0||MCnn_2-0: Port Power Allocation bits. These bits set the maximum power classification level that a given Port (2-Pair or 4-Pair) is allowed to power on
In Semi Auto mode these bits need to be set prior to issuing a PWONn command, while in Auto mode these bits need to be set prior to setting the DETE and CLE bits in 0x14.
|1||0||1||1||4-Pair 30W (Class 4)|
|1||1||0||0||4-Pair 45W (Class 5)|
|1||1||0||1||4-Pair 60W (Class 6)|
|1||1||1||0||4-Pair 75W (Class 7)|
|1||1||1||1||4-Pair 90W (Class 8)|
In order to prevent any unexpected behavior the setting the 4PWnn bits should only be done immediately following a Power On Reset (POR) event while the ports are still in OFF mode.
The Power Allocation (0x29h) value needs to be set prior to issuing a PWON command in Semi Auto or Auto modes, and prior to setting the DETE and CLE bits in Auto mode. Any changes to the Power Allocation value after a PWON command is given may be ignored.
For 4-pair dual signature PDs, the odd numbered Channels takes priority over the even numbered Channels. Thus, an even numbered Channel will be powered based on the difference between the total power allocated and what the odd Channel classified as.
For example if a dual signature PD contained two 45W PDs and the PSEs power allocation was set to 60W, the odd numbered Channel will be powered at 45W while the even numbered Channel will be limited to 15W.
For 2-Pair wired ports, the MCnn_2-0 bits set the power allocation settings for both channels 1 and 2 and 3 and 4 concurrently.
It is possible to have channels 3 and 4 set to 15.4W while channels 1 and 2 are set to 30W, but it is not possible to have different power allocation settings between channels 1 and 2 or 3 and 4