UART/IrDA Control and Status Registers
12-79
UART Devices
The frame lengths of received frames are written into the status FIFO. This
information can be read by reading the status FIFO registers (SFREGL and
SFREGH—these registers do not physically exist). The least significant bits
are read from SFREGL, and the most significant bits are read from SFREGH.
Reading these registers does not alter the status FIFO read pointer. These
registers must be read before the pointer is incremented by reading the
SFLSR.
In terms of the IrDA frame format (see Figure 12–14), the value read in the
SFREGH/SFREGL registers is the byte length from A to CRC.
Table 12–80. Status FIFO Register Low (SFREGL)
Bit
Name
Function
R/W
Reset
Value
7–0
SFREGL
LSB part of the frame length
R
Undefined
Table 12–81. Status FIFO Register High (SFREGH)
Bit
Name
Function
R/W
Reset
Value
7–4
–
Reserved
R
0000
3–0
SFREGH
MSB part of the frame length
R
Undefined
The beginning of frame control register (BLR) [6] selects whether 0xC0 or
0xFF start patterns are to be used and when multiple start flags are required
in SIR mode. If only one start flag is required, this is always 0xC0. If n start flags
are required, then either (n - 1) C0x0 or (n - 1) 0xFF flags are sent, followed by
a single 0xC0 flag (immediately preceding the first data byte).
Table 12–82. BOF Control Register (BLR)
Bit
Name
Value
Function
R/W
Reset
Value
7
STS_FIFO_RESET
Status FIFO reset. This bit is self-clearing
R/W
0
6
XBOF_TYPE
SIR XBOF select
R/W
1
0
0xFF
1
0xC0
5–0
–
Reserved
R/W
000000