25
Maxim Integrated
16-Bit Microcontrollers with
Infrared Module and Optional USB
MAXQ612/MAXQ622
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 event.
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 is generated, if
enabled. The IR module continues to operate in receive
mode until it is stopped by switching into transmit mode
or clearing IREN = 0.
Carrier Burst-Count Mode
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 determination.
Once the frequency has been determined, the IR receive
function can be reduced to counting the number of car-
rier pulses in the burst and the duration of the combined
mark-space time within the burst. To simplify this pro-
cess, the receive burst-count mode can be used. When
RXBCNT = 0, the standard IR receive capture function-
ality is in place. When RXBCNT = 1, the IRV capture
operation is disabled and the interrupt flag associated
with the capture no longer denotes a capture. In the
carrier burst-count mode, the IRMT register only counts
qualified edges. The IRIF interrupt flag now sets if two
IRCA cycles elapse without getting a qualified edge. The
IRIF interrupt flag thus denotes absence of the carrier
and the beginning of a space in the receive signal. The
IRCFME bit is still used to define whether the IRV register
is counting system IRCLK clocks or IRCA-defined carrier
cycles. The IRXRL bit defines whether the IRV register
is reloaded with 0000h on detection of a qualified edge
(per the IRXSEL[1:0] bits).
16-Bit Timers/Counters
The microcontroller provides two general-purpose tim-
ers/counters that support the following functions:
16-bit timer/counter
16-bit up/down autoreload
Counter function of external pulse
16-bit timer with capture
16-bit timer with compare
Input/output enhancements for pulse-width modulation
Set/reset/toggle output state on comparator match
Prescaler with 2n divider (for n = 0, 2, 4, 6, 8, 10)
General-Purpose I/O
The microcontroller provides port pins for general-pur-
pose I/O that have the following features:
CMOS output drivers
Schmitt trigger inputs
Optional weak pullup to VDD when operating in input
mode
While the microcontroller is in a reset state, all port pins
become three-state with both weak pullups and input
buffers disabled, unless otherwise noted.
From a software perspective, each port appears as a
group of peripheral registers with unique addresses.
Special function pins can also be used as general-pur-
pose I/O pins when the special functions are disabled.
For a detailed description of the special functions avail-
able for each pin, refer to the IC-specific user’s guide,
e.g., the MAXQ622 User’s Guide describes all special
functions available on the MAXQ612/MAXQ622.
Serial Peripherals
The microcontroller supports two independent USARTs,
two SPI master/slave communications ports, and an I2C
bus.
USART
The USART units are implemented with the following
characteristics:
2-wire interface
Full-duplex operation for asynchronous data transfers
Half-duplex operation for synchronous data transfers
Programmable interrupt for receive and transmit
Independent baud-rate generator
Table 3. USART Mode Details
MODE
TYPE
START BITS
DATA BITS
STOP BITS
Mode 0
Synchronous
N/A
8
N/A
Mode 1
Asynchronous
1
8
1
Mode 2
Asynchronous
1
8 + 1
1
Mode 3
Asynchronous
1
8 + 1
1