NXP Semiconductors PN544 C2 - CLK Request in NFC Active Target Mode

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 67 of 172
9.4.5 CLK request in NFC active target mode
In NFC active reader mode the clock request usage is illustrated:
(1) ATR_RES has to be in-time to serve an ATR_REQ
Fig 41. NFC CLK request in NFC active target mode
Initiator expects response after:
StdATRguardtimeInitiator
TTTT
+
+=
T
Guardtime
is equal or greater 5ms (according ISO specification)
T
STD
is between 57us and 302us
T
ATR
is between 510us and 1,7ms (no general bytes, all data rates)
The target is able to respond earliest after:
321
arg
tttT
etT
++
=
t1 is between 100us and 1ms (depending on power state)
t2 depends on the settling time of the clock source and the time-out derived
t3 is between 2,5ms and 4ms
To build a functional system T
Target
must be smaller than T
Initiator
!