mfrc500 NXP Semiconductors, mfrc500 Datasheet - Page 79

• Manufacturer Part Number: mfrc500
• Description: Highly Integrated Iso14443a Reader Ic
• Manufacturer: NXP Semiconductors

Philips Semiconductors
Highly Integrated ISO 14443A Reader IC
9.2.4
The TRunning bit in the SecondaryStatus Register shows the timer’s current status. Any configured start
event starts the timer at the TReloadValue and changes the status flag TRunning to 1, any configured stop
event stops the timer and sets the status flag TRunning back to 0. As long as status flag TRunning is set to
1, the TimerValue Register changes with the next timer unit clock.
The actual timer unit content can be read directly via the TimerValue Register.
9.3
9.3.1
Having started the timer by setting TReloadValue the timer unit decrements the TimerValue Register
beginning with a certain start event. If a certain stop event occurs e.g. a bit is received from the card, the
timer unit stops (no interrupt is generated).
On the other hand, if no stop event occurs, e.g. the card does not answer in the expected time, the timer unit
decrements down to zero and generates a timer interrupt request. This signals the µ-Processor that the
expected event has not occurred in the given time T
9.3.2
The time T
the MF RC500 timer unit. Setting TReloadValue the timer starts to decrement. If the defined stop event
occurs the timers stops. The time between start and stop can be calculated by
if the timer does not decrements down to zero.
9.3.3
The µ-Processor starts the timer unit and waits for the timer interrupt. After the specified time T
interrupt will occur.
9.3.4
If the µ-Processor sets bit TAutoRestart, it will generate an interrupt request periodically after every T
Usage of the Timer Unit
STATUS OF THE TIMER UNIT
TIME-OUT- AND WATCH-DOG-COUNTER
STOP WATCH
PROGRAMMABLE ONE-SHOT TIMER
PERIODICAL TRIGGER
Timer
between a certain start- and stop event may be measured by the µ-Processor by means of
Δ
T
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(
T
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load
value
Timer
79
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.
Timer
Product Specification Rev. 3.2;December 2005
value
)
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T
Timer
MF RC500
Timer
PUBLIC
Timer
.
the