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 19 of 172
U-Frames coding
The unnumbered (U) format commands and responses are used to extend the number of
data link control functions. The unnumbered format frames have 5 modifier bits which
allow for up to 32 additional commands and responses. Only a subset of the HDLC
commands and responses are used for SHDLC:
RSET: Reset of the data link layer is used to reset the sequence number variables in the
both endpoints.
UA: Unnumbered Acknowledgment is used to acknowledge the receipt and acceptance
of a RSET command.
Table 8. modifier coding of the U-Frames
Frames modifier status
RSET 11001 Mandatory
UA 00110 Mandatory
The optional command UI is not supported.
7.4.3.3 RSET Frame
The RSET co
mmand is used to reset the link status. The behavior is the same as
described in the respective SWP specification [2].
1111 1001 nnnn nnnn
8 bits 8 bits
RSET
Window
size
b
8
...b
1
Endpoint
capabilities
8 bits
2 nnnn nnnn 4
(1) Window size = 4 for PN544
Fig 9. RSET Frame
WARNING: Before initiating an HCI communication with PN544, at Power up,
or after a Reset (VEN), it is mandatory to send a RSET frame. The recommended
frame is defined in the following figure:
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