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• Program the CWT_VAL register to the value that needs to be enforced
• Activate CWT function by setting the CWT_EN bit in the CTRL register
• Enable the CWT_ERR interrupt by clearing the CWT_IM bit in the INT_MASK
register
• If an interrupt occurs, then the software should read the RX_STATUS register to
determine if the error was caused by a CWT_ERR violation. The software should
clear the CWT_ERR interrupt by writing a “1” to the CWT_ERR bit in the
RX_STATUS register
• Software can disable the CWT counter by clearing the CWT_EN bit in the CTRL
register at any time
21.6.7.3 Block Wait Time and Block Guard Time
A 32-bit timer is used to measure both Block Wait Time (BWT) and Block Guard Time
(BGT). The BWT and BGT timer are used to measure the delay between the leading edge
of the last character of the block received by the card and the leading edge of the first
character of the next block sent by the card. If this time measured is larger than the value
in BWT_VAL register, then the BWT_ERR flag will be set and an interrupt generated. If
the time is less than the value in the BGT_VAL register, then the BGT_ERR flag will be
set and an interrupt generated. The block wait timer can be configured as follows:
• Program the BWT_VAL and BGT_VAL registers to the value that need to be
enforced
• Activate the block wait timer by writing '1' to BWT_EN bit in the CTRL register
• Enable the BWT_ERR and BGT_ERR interrupts by clearing the BWT_IM and
BGT_IM bits in the INT_MASK register
• If an interrupt occurs, then the software should read the RX_STATUS register to
determine if the error was caused by a BWT_ERR or BGT_ERR violation. The
software should clear the interrupt status bit by writing a “1” to the BWT_ERR bit or
BGT_ERR, respectively, in the RX_STATUS register
• Software can disable the BWT counter by clearing the BWT_EN bit in the CTRL
register at any time
NOTE
BWT should be enabled after all bytes are written to in Tx
FIFO. This is necessary to avoid the condition where writes to
Tx FIFO are very slow (more than 1 ETU time apart) and if
BWT is enabled earlier, then BWT error can trigger falsely.
Functional Description
K32 L2A Reference Manual, Rev. 2, 01/2020
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NXP Semiconductors
Содержание K32 L2A Series
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