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W5500 Datasheet Version1.0.9

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the TCP packet is retransmitted. The retransmission is repeated as many as ‘RCR+1’.

Even after TCP retransmission is repeated as ‘RCR+1’ and there is no response to the

TCP retransmission, the final timeout is occurred and Sn_IR(TIMEOUT) becomes ‘1’.

The time of final timeout (TCPTO) of TCP retransmission is as below.

�� = (∑(�� × 2��) + ((�� − ��) × ��)

��

��=0

) × 0.1��

N : Retransmission count, 0≤N ≤ M

M : Minimum value when RTR x 2(M+1) > 65535 and 0 ≤ M ≤ RCR

RTRMAX : RTR x 2M

Ex) When RTR = 2000(0x07D0), RCR = 8(0x0008),

ARPTO = 2000 X 0.1ms X 9 = 1800ms = 1.8s

TCPTO = (0x07D0+0x0FA0+0x1F40+0x3E80+0x7D00+0xFA00+0xFA00+0xFA00+0xFA00) X 0.1ms

= (2000 + 4000 + 8000 + 16000 + 32000 + ((8 - 4) X 64000)) X 0.1ms

= 318000 X 0.1ms = 31.8s

PTIMER (PPP Link Control Protocol Request Timer Register) [R/W] [0x001C] [0x0028]

PTIMER configures the time for sending LCP echo request. The unit of time is 25ms.

Ex) in case that PTIMER is 200,

200 * 25(ms) = 5000(ms) = 5 seconds

PMAGIC (PPP Link Control Protocol Magic number Register) [R/W] [0x001D] [0x00]

PMAGIC configures the 4bytes magic number to be used in LCP echo request.

Ex) PMAGIC = 0x01

0x001D

0x01

LCP Magic number = 0x01010101

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