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NXP Semiconductors
UM191812
PN544 C2 User Manual
191812
All information provided in this document is subject to legal disclaimers.
© NXP B.V. 2010. All rights reserved.
User Manual
Rev. 1.2 — 2010-06-16
15 of 172
The LLC Length specifies the length of the frame to follow. The length itself is not
counted. The two CRC bytes are counted. The LLC frame is represented as follows:
•
LLC Length is mandatory (valid range: 03h – 20h)
•
LLC Header is mandatory.
•
LLC Payload is optional. This is depending on the LLC command, which is
contained in the LLC Header.
•
CRC is always present
the bit and byte order is Most Significant Bit / Byte first.
7.4.2 Chaining description
For HCI command, the format of a HCP packet is defined in Fig 5:
(1) CB is the chaining bit and its value is equal to 1 except when message fragmentation is used
(2) P
ID
specifies the pipe identifier.
Fig 5. HCP packet
The LLC layer does not provide any chaining, segmentation or reassembly feature.
Therefore the HCI has to obey the maximum size rules as defined in this document.
If HCI determines that a certain HCI command does not fit into the negotiated packet
size, HCI needs to split up the big packet into smaller chunks by using the chaining
feature as specified in HCI. The LLC is and shall not be aware of this chaining
functionality. LLC does not care if a packet is split up into one or more LLC frames.
The length of the LLC frame is aligned with the length of the HCI packet. There is no
padding at the end of the HCI packet. When HCI is sent over LLC, the beginning of an
LLC frame implies the beginning of an HCI packet (without considering the LLC header),
the end of an LLC frame implies the end of an HCI packet (without considering the CRC).