GMS30C7201 Datasheet, PDF (171/352 Pages) Hynix Semiconductor – 60MHz operation frequency Low power consumption

Fast AMBA Peripherals
12.3 Medium and Fast Infrared Module
12.3.1 Overview
The ARM 7201 Infrared Interface Module implements in hardware the physical layer of an
infrared serial port, compliant with Version 1.1 of the Infrared Data Association (IrDA)
standard. Communication speeds of up to 4Mbit/s are supported. When combined with
analogue transducer components, it provides a complete interface between infra-red media and
an AMBA-compliant peripheral bus (APB).
The module comprises three separate encoder/decoder units for implementing three different
combinations of modulation scheme and data encoding system defined by the IrDA standard.
These are called the Slow-, Medium- and Fast-infrared encoder/decoders.
SIr, MIr and FIr
The Slow Encoder/Decoder (SIr) is used to modulate and demodulate serial data only, using the
Hewlett-Packard Serial Infrared standard (HP-SIR) for bit encoding. Serial transmit data from
a UART (external to the Ir Interface Module) is modulated using return-to-zero (RTZ) encoding
to produce an output to drive the IR transmitter LED, while data received from the IR detector
is converted into a serial bit stream to drive the UART serial input. The SIr supports data rates
of up to 115.2kbit/s.
The Medium Speed Encoder/Decoder (MIr) encodes/decodes peripheral bus data according to
a modified HDLC standard, using flag characters, bit-stuffing and a 16-bit CRC checker. RTZ
modulation and demodulation of the encoded data stream takes place in the same way as for the
SIr. Two signal bit rates are specified: 0.576Mbit/s and 1.152Mbit/s. MIr data and control bytes
are memory mapped via the ARM 7201 fast APB.
The Fast Speed Encoder/Decoder (FIr) operates at a fixed bit rate of 4Mbit/s. Modulation/
demodulation is by a phase shift key scheme called pulse position modulation (4PPM) that uses
one of four signalling symbols to represent each pair of data bits. Data encoding uses a packet
format that prefixes bit- and symbol-synchronization flags to data and appends a 32-bit CRC
and stop flag to the end of each packet. The start and stop flags use signalling symbols that are
not used to encode data and hence bit-stuffing of data is not required in this mode. The FIr also
interfaces to the ARM 7201 fast APB.
Only one of the Encoder/Decoder modules can be enabled to transmit and receive data from the
IrDA transducers at one time. Selection of an Ir sub-module is by means of the IrEnable register.
Accordingly the MIr and FIr sub-modules can be regarded by programmers as independent
entities which are operated using common control and data registers, but which report status
data via separate read registers.
Detailed descriptions of the MIr and FIr are given in the following sections. The SIr however
has no data or control register associated with it, and interfaces directly to the UART serial
streams. Accordingly with the exception of the Ir Enable register, it has no presence on the
memory map nor an interface to the APB.
12.3.2 Common Register Description
The Infrared Interface module uses a single mode register, IrEnable, to select which infrared
interface module is selected. The Medium and Fast modules share a common control and data
interface while maintaining separate status registers. The common registers used by both the FIr
and MIr blocks are described below.
GMS30C7201 Data Sheet
12-17