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 62 of 172
The request & release mechanism using CLKREQ pin is described in the following figure:
Fig 36. Clock request with CLKREQ pin
Step1: As soon as the PN544 needs system clock, it puts the CLKREQ level to high.
Then system has to provide the clock. The acknowledgement from Host to PN544 is
detailed in the ‘clock acknowledge’ chapter.
Step2: As soon as the PN544 does not need the system clock, it puts the CLKREQ
level to low. Then system can disable the clock.
9.4.3.3 Request through NXP_EVT_CLK_REQUEST event
In this mode,
PN544 will request the clock by sending an HCI event to the Host
Controller. To setup such a configuration, the following EEPROM area has to be set:
Table 54. Setting for clock request with HCI event
Name Length
(bytes)
Value(s) Comments
PlClockRequest 1 0x02 PN544 will request clock
from system by using an
HCI proprietary event
The request & release mechanism using NXP_EVT_CLK_REQUEST HCI event is
described in the following figure:
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