Product data

MFRC631 All information provided in this document is subject to legal disclaimers. © NXP B.V. 2014. All rights reserved.
Product data sheet
COMPANY PUBLIC
Rev. 3.3 — 4 February 2014
227433 79 of 120
NXP Semiconductors
MFRC631
High performance ISO/IEC 14443 A/B reader solution
9.7.2.21 T4ReloadHi
High byte of the reload value of the 16-bit timer 4.
9.7.2.22 T4ReloadLo
Low byte of the reload value of the 16-bit timer 4.
Table 112. T4Control bits
Bit Symbol Description
7 T4Running Shows if the timer T4 is running. If the bit T4StartStopNow is set, this
bit and the timer T4 can be started/stopped.
6T4Start
StopNow
if set, the bit T4Running can be changed.
5 T4AutoTrimm If set to one, the timer activates an LFO trimming procedure when it
underflows. For the T4AutoTrimm function, at least one timer (T0 to
T3) has to be configured properly for trimming (T3 is not allowed if
T4AutoLPCD is set in parallel).
4 T4AutoLPCD If set to one, the timer activates a low-power card detection
sequence. If a card is detected an interrupt request is raised and the
system remains active if enabled. If no card is detected the
MFRC631 enters the Power down mode if enabled. The timer is
automatically restarted (no gap). Timer 3 is used to specify the time
where the RF field is enabled to check if a card is present. Therefor
you may not use Timer 3 for T4AutoTrimm in parallel.
3 T4AutoRestart Set to logic 1, the timer automatically restarts its countdown from
T4ReloadValue, after the counter value has reached the value zero.
Set to logic 0 the timer decrements to zero and stops. The bit
Timer4Irq is set to logic 1 at timer underflow.
2 T4AutoWakeUp If set, the MFRC631 wakes up automatically, when the timer T4 has
an underflow. This bit has to be set if the IC should enter the Power
down mode after T4AutoTrimm and/or T4AutoLPCD is finished and
no card has been detected. If the IC should stay active after one of
these procedures this bit has to be set to 0.
1 to 0 T4Clk 00b - the timer input clock is the LFO clock
01b - the timer input clock is the LFO clock/8
10b - the timer input clock is the LFO clock/16
11b - the timer input clock is the LFO clock/32
Table 113. T4ReloadHi register (address 24h)
Bit 7 6 5 4 3 2 1 0
Symbol T4ReloadHi
Access
rights
r/w
Table 114. T4ReloadHi bits
Bit Symbol Description
7 to 0 T4ReloadHi Defines high byte of the for the reload value of timer 4. With the start
event the timer 4 loads the T4ReloadVal. Changing this register affects
the timer only at the next start event.