MAXQ610 Maxim, MAXQ610 Datasheet - Page 17

• Manufacturer Part Number: MAXQ610
• Description: The MAXQ610 is a low-power, 16-bit MAXQ® microcontroller designed for low-power applications including universal remote controls, consumer electronics, and white goods
• Manufacturer: Maxim

On the next qualified event, the IR module does the
following:
1) Captures the IRRX pin state and transfers its value to
2) Transfers its current IRV value to the IRMT.
3) Resets IRV content to 0000h (if IRXRL = 1).
4) Continues counting again until the next qualified
If the IR timer value rolls over from 0FFFFh to 0000h
before a qualified event happens, the IR timer overflow
(IROV) flag is set to 1 and an interrupt generated if
enabled. The IR module continues to operate in receive
Figure 6. Receive Burst-Count Example
IRDATA. If a falling edge occurs, IRDATA = 0. If a
rising edge occurs, IRDATA = 1.
event.
1
TO
IRMT
IRRX
IRV
4
5
6
7
8
9
16-Bit Microcontroller with Infrared Module
CAPTURE INTERRUPT (IRIF = 1).
IRV ≥ IRMT.
IRV = 0 (IF IRXRL = 1).
SOFTWARE SETS IRCA = CARRIER FREQUENCY.
SOFTWARE SETS RXBCNT = 1 (WHICH CLEARS IRMT = 0001 IN HARDWARE).
SOFTWARE CLEARS IRCFME = 0 SO THAT IRV COUNTS CARRIER CYCLES. IRV IS RESET TO 0 ON QUALIFIED EDGE DETECTION IF IRXRL = 1.
SOFTWARE ADDS TO IRMT THE NUMBER OF PULSES USED FOR CARRIER MEASUREMENT.
IRCA x 2x COUNTER FOR SPACE CAN BEGIN IMMEDIATELY (QUALIFIED EDGE RESETS).
QUALIFIED EDGE DETECTED: IRMT++
IRV RESET TO 0 IF IRXRL = 1.
IRCA x 2 PERIOD ELAPSES: IRIF = 1; CARRIER ABSENCE = SPACE.
BURST MARK = IRMT PULSES.
SOFTWARE CLEARS RXBCNT = 0 SO THAT WE CAPTURE ON THE NEXT QUALIFIED EDGE.
QUALIFIED EDGE DETECTED: IRIF = 1, CAPTURE IRV ≥ IRMT AS THE BURST SPACE (PLUS UP TO ONE CARRIER CYCLE).
SOFTWARE SET RXBCNT = 1 AS IN (5).
CONTINUE (5) TO (8) UNTIL LEARNING SPACE EXCEEDS SOME DURATION. IRV ROLLOVERS CAN BE USED.
CARRIER FREQUENCY
CALCULATION
1
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2
3
4
5
6
IRMT = PULSE COUNTING
7
IRV = CARRIER CYCLE COUNTING
mode until it is stopped by switching into transmit mode
(IRMODE = 1) or clearing IREN = 0.
A special mode reduces the CPU processing burden
when performing IR learning functions. Typically, when
operating in an IR learning capacity, some number of
carrier cycles are examined for frequency determina-
tion. Once the frequency has been determined, the IR
receive function can be reduced to counting the number
of carrier pulses in the burst and the duration of the
combined mark-space time within the burst. To simplify
this process, the receive burst-count mode (as enabled
by the RXBCNT bit) can be used. When RXBCNT = 0,
the standard IR receive capture functionality is in place.
Carrier Burst-Count Mode
IRMT = PULSE COUNTING
8
9
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