K60P100M100SF2RM Datasheet, PDF (1554/1809 Pages) Freescale Semiconductor, Inc – K60 Sub-Family Reference Manual

Functional description
51.4.7.6 UART restrictions in ISO-7816 operation
Due to the flexibility of the UART module, there are several features and interrupts that
are not supported while running in ISO-7816 mode. These restrictions are documented
within the register bit definitions.
51.4.8 Infrared interface
The UART provides the capability of transmitting narrow pulses to an IR LED and
receiving narrow pulses and transforming them to serial bits, which are sent to the
UART. The IrDA physical layer specification defines a half-duplex infrared
communication link for exchanging data. The full standard includes data rates up to 16
Mbits/s. This design covers data rates only between 2.4 kbits/s and 115.2 kbits/s.
The UART has an infrared transmit encoder and receive decoder. The UART transmits
serial bits of data which are encoded by the infrared submodule to transmit a narrow
pulse for every zero bit. No pulse is transmitted for every one bit. When receiving data,
the IR pulses are detected using an IR photo diode and transformed to CMOS levels by
the IR receive decoder (external from the MCU). The narrow pulses are then stretched by
the infrared receive decoder to get back to a serial bit stream to be received by the UART.
The polarity of transmitted pulses and expected receive pulses can be inverted so that a
direct connection can be made to external IrDA transceiver modules that use active low
pulses.
The infrared submodule receives its clock sources from the UART. One of these two
clocks are selected in the infrared submodule in order to generate either 3/16, 1/16, 1/32
or 1/4 narrow pulses during transmission.
51.4.8.1 Infrared transmit encoder
The infrared transmit encoder converts serial bits of data from transmit shift register to
the TXD signal. A narrow pulse is transmitted for a zero bit and no pulse for a one bit.
The narrow pulse is sent in the middle of the bit with a duration of 1/32, 1/16, 3/16 or 1/4
of a bit time. A narrow high pulse is transmitted for a zero bit when C3[TXINV] is
cleared, while a narrow low pulse is transmitted for a zero bit when C3[TXINV] is set.
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K60 Sub-Family Reference Manual, Rev. 6, Nov 2011
Freescale Semiconductor, Inc.