Intel PXA255 - Manual (Page 396)

11-12 Intel® PXA255 Processor Developer’s Manual
Fast Infrared Communication Port
11.3.4 FICP Data Register (ICDR)
The ICDR, shown in Table 11-5 , is a 32-bit register and its lower 8 bits are the top entry of the
transmit FIFO when the register is written and the bottom entry of the receive FIFO when the
register is read.
Reads to ICDR access the lower 8 bits of the receive FIFO’s bottom entry. As data enters the top of
the receive FIFO, bits 8 – 10 are used as tags to indicate conditions that occur as each piece of data
is received. The tag bits are transferred down the FIFO with the data byte that encountered the
condition. When data reaches the bottom of the FIFO, bit 8 of the FIFO entry is transferred to the
end-of-frame (EOF) flag, bit 9 to the CRC error (CRE) flag, and bit 10 to the receiver overrun
(ROR) flag. All these flags are in FICP status register 1. These flags can be read to determine
whether the value at the bottom of the FIFO represents the frame’s last byte or an error that was
encountered during reception. After the flags are checked, the FIFO value can be read. This causes
the data in the next location of the receive FIFO to be transferred to the bottom entry and its EOF,
CRE, and ROR bits to be transferred to the status register.
The end/error in FIFO (EIF) flag is set in status register 0 when a tag bit is set in any of the receive
FIFO’s bottom eight, 16, or 32 entries, as determined by the trigger level. The EIF flag is cleared
when no error bits are set in the FIFO’s bottom entries. When EIF is set, an interrupt is generated
and the receive FIFO DMA request is disabled. Software must empty the FIFO and check for the
EOF, CRE, and ROR error flags in ICSR1 before it removes each data value from the FIFO. After
each entry is removed, the EIF bit must be checked to determine if any set end or error tag remains
and the procedure is repeated until all set tags are flushed from the FIFO’s bottom entries. When
EIF is cleared, DMA service for the receive FIFO is re-enabled.
Both FIFOs are cleared when the processor is reset. The transmit FIFO is cleared when TXE is 0.
The receive FIFO is cleared when RXE is 0.
This is a read/write register. Ignore reads from reserved bits. Write zeros to reserved bits.
Table 11-5. ICRD Bit Definitions
0x4080_000C
Fast Infrared Communication Port
Data Register (ICDR)
Fast Infrared Communication Port
Bit 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
reserved DATA
Reset 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
Bits Name Description
[31:8] — reserved
[7:0] DATA
Top/bottom of transmit/receive FIFO.
Read - Read data from front of receive FIFO
Write - Place data at end of transmit FIFO