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NXP Semiconductors
UM191812
PN544 C2 User Manual
191812
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© NXP B.V. 2010. All rights reserved.
User Manual
Rev. 1.2 — 2010-06-16
25 of 172
7.4.5.2 Guard Host Timeout
This timeout defines the maximum time the Host has to acknowledge a frame received.
When timeout is reached, PN544 resends the frame. It is used with HSU interface.
(1) T: Guard Timeout Host
Fig 17. PN544 Guard Host Timeout
Case Communication OK:
After sending a frame to the host PN544 starts an internal
timer, waiting for the frame to be acknowledged by the host. The ACK is received in-time
and PN544 will proceed sending the next frame.
Case Communication KO:
Timer is started after frame was sent but no ACK is
received in-time. -> Timeout triggers PN544 to resend the frame to the host.
The number of retries is defined in EEPROM as Host_Rx_Retry and Host_Tx_Retry.
Guard Host Timeout value can be changed by setting the
GuardHostTimeoutMSB &
GuardHostTimeoutLSB
EEPROM area. (See
HW configuration
chapter).
Note: To disable the resend mechanism, the timeout has to be set to NULL value.