4-Port PoE Manager

Microsemi Proprietary and Confidential. PD69104B1/F Datasheet Revision 2.0

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The following illustration shows the header bit width.

Figure 9 • Header Bit Width

3.15.4

Timeout Mechanisms

The UART protocol has a frame timeout mechanism. This mechanism has the following two purposes.

Distinguishing between the frame's suffix of 8'f5 and a payload byte with the same value. The

mechanism identifies a frame suffix only when it arrives as 2 bytes in a read access or as 4-bytes in a

write access; otherwise it is treated as a data byte.

Preventing UART communication from getting stuck. A 1-second timeout counter is activated

beginning with a start frame (the end of header byte) till a suffix arrival. If a suffix byte does not

arrive within that time the transaction is ignored and the slave moves into an IDLE state.

The following illustration shows the timeout mechanism.

Figure 10 • Timeout Mechanism