NXP Semiconductors PN544 C2 - Page 18

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 18 of 172
Where:
- N(S): Number of the information frame
- N(R): Number of next information frame to receive
- TYPE: Type of S-Frame
- M: Modifier bits for U-Frame
I-Frames coding
The functions of the information(I) command and response is to transfer sequentially
numbered frames, each containing an information field, which might be empty, across the
data link.
S-Frames coding
Supervisory(S) commands and responses are used to perform numbered supervisory
functions such as acknowledgment, temporary suspension of information transfer, or
error recovery. Frames with the S format control field do not contain an information field.
Supervisory Format commands and responses are as follows:
RR: Receive Ready is used by an endpoint to indicate that it is ready to receive an
information frame and/or acknowledge previously received frames.
RNR: Receive Not Ready is used to indicate that an endpoint is not ready to receive any
information frames or acknowledgments.
REJ: Reject is used to request the retransmission of frames.
SREJ: This optional command is not supported by the PN544. If received SREJ is
treated like an erroneous frame.
The type coding is given by the following table:
Table 7. Type coding of the S-Frames
Frames type status
RR 00 Mandatory
REJ 01 Mandatory
RNR 10 Mandatory
SREJ 11 Not supported
Optional type of frame shall not be used before capability negotiation is defined during
initialization.