DP83822I: status register related question

Here are your answers:

should customer read BMSR register before PHYSTS register to update PHYSTS?

[ross] yes.

Q1.0x0001 Basic Mode Status Register (BMSR)

let me confirm that this register would be changed once "read".

its default is 0. correct ?

[ross] yes. it is a LL (latch-low). you must read this register twice to get the current link status. this is documented in the datasheet.

in case Customer doesnt read BMSR , what PHY Status Register (PHYSTS) Bit 0 Link Status will be?

[ross] PHYSTS as documented in the datasheet will reflect the same value in BMSR. You must read BMSR to update PHYSTS.

pattern 1

customer inserts the cable into their system and make their system wake up

will link status bit 0 be 1?

[ross] No, you must read the register to clear the LL. Once you read it twice and there is a link established the bit will be set to 0b1. Just because the system wakes up does not mean a link is established.

pattern 2

they put the cable off from their system

will link status bit 0 be 0?

[ross] Yes, if link is dropped and detected the bit will change to 0b0. 

Pattern 3

they re-connect and insert the cable into their system.

will link status bit 0 be 0?

[ross] the first read will be 0b0 because of the LL. You have to read the register twice to get the current link status.

Q2

will PHYSTS bit be 0 if customer doesnt read the bit on BMSR?

[ross] yes. you need to read BMSR to update bit[0] in PHYSTS.