GMS30C7201 Datasheet, PDF (194/352 Pages) Hynix Semiconductor – 60MHz operation frequency Low power consumption

Fast AMBA Peripherals
12.9 Fast Infrared Port (FIr)
The Fast Infrared port (FIr) operates at half-duplex and provides direct connection to
commercially available Infrared Data Association (IrDA) compliant LED transceivers. The FIr
supports the 4.0Mbps IrDA standard, using four pulse position modulation (4PPM) and a
specialized serial packet protocol developed expressly for IrDA transmission.
High Speed FIr Operation
Before enabling the FIr for high-speed operation, the user must first clear any writable or
“sticky” status bits which are set by writing a one to each bit. Next, the desired mode of
operation is programmed in the control registers. At this point the user may “prime” the FIr’s
transmit buffer by writing the first data word, or the buffer can remain empty and either
programmed I/O or the DMA may be used to service it after the FIr is enabled. Once the FIr is
enabled, transmission/reception of data can begin on the transmit and receive pins. The FIr’s
frame formats are outlined below.
4PPM Modulation
Four position pulse modulation (4PPM) is used for the high-speed transmission rate of
4.0Mbps. Payload data is divided into data bit pairs (DBPs) for encoding with LSBs transmitted
first. Each DBP is represented by one of four symbols (DDs) comprising a single 125ms pulse
within a 500ms symbol period. The 125ms quarters of a symbol are known as “chips”. The
resulting signal waveform for the four data DDs is shown in Figure 12-11: 4PPM Modulation
Encoding. Figure 12-12: 4PPM Modulation Example on page 12-41 shows an example of
4PPM modulation of the byte, 0b10110001 which is constructed using four DBPs. Note that bits
within each DBPare not reordered, but the least significant DBP is transmitted first.
Two-bit Symbol
Chip
1
2
3
4
DBP = 00
DBP = 01
DBP = 10
DBP = 11
Figure 12-11: 4PPM Modulation Encoding
12-40
GMS30C7201 Data Sheet