CLRC632 Datasheet, PDF (121/163 Pages) NXP Semiconductors – Multiple Protocol Contactless Reader IC

Philips Semiconductors
Multiple Protocol Contactless Reader IC
Product Specification Rev. 3.0; May 2003
CL RC632
18.4.2.4 Receiving Bit Oriented Frames
The receiver can handle byte streams with incomplete bytes, resulting in bit oriented frames. To support this,
the following values may be used:
• RxAlign selects a bit offset for the first incoming byte, e.g. if RxAlign is set to 3, the first 5 bits received
are forwarded to the FIFO buffer. Further bits are packed into bytes and forwarded. After reception,
RxAlign is cleared automatically.
If RxAlign is set to zero, all incoming bits are packed into one byte.
• RxLastBits returns the number of bits valid in the last received byte, e.g. if RxLastBits evaluates to 5 at
the end of the receiving command, the 5 least significant bits are valid.
RxlastBits evaluates to zero if the last byte is complete.
RxLastBits is valid only, if no frame error is indicated by the flag FrameErr. If RxAlign is set to a value other
than zero and also ParityEn is active, the first parity bit is not checked but ignored.
18.4.2.5 Communication Errors
The following table shows which event causes the setting of error flags:
Cause
Received data did not start with a SOF pattern.
The CRC block is not equal the expected value.
The received data is shorter than the CRC block.
The parity bit is not equal the expected value (e. g. a bit collision occurs when a parity is expected)
A collision is detected.
Table 18-3: Communication Error Table
Bit, that is set
FramingErr
CRCErr
CRCErr
ParErr
CollErr
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