IRCC SMSC Corporation, IRCC Datasheet - Page 22

• Manufacturer Part Number: IRCC
• Description: INFRARED COMMUNICATIONS CONTROLLER
• Manufacturer: SMSC Corporation

4PPM BOF Counting
The IrCC can account for system-dependent
limitations such as long interrupt latencies and
transceiver stabilization times by increasing the
number of PA flags at the beginning of every
4PPM frame (Figure 16).
The BOF COUNT register contains the number
CCITT 16-bit
CRC
PA (#1)
FCS
Previous
Frame
'01111110'
...
binary
STO
Appends 0 - 4095 PA Bytes
to Beginning of Frame
PA (#16)
BOF COUNT register
FIGURE 15 - BRICK WALLED HDLC FRAMES
'01111110'
binary
STA
FIGURE 16 - 4PPM EXTENDED BOF
Inserts 0 - 4095 Flags between
8-bit Start
'01111110'
Field
STA
Brick Walled Frames
BW COUNT register
binary
STA
8-bit Address
8-bit Address
22
ADDR
Field
ADDR
Field
of additional PA bytes that are to be appended to
the standard 4PPM BOF characters.
NOTE: the BOF COUNT extensions only apply
to messages that start from an idle line state; i.e.,
BOF counting does not apply to brick walled
messages.
Brick Walled Frame
8-bit Control field plus up to 2K - 3 bytes
8-bit Control field plus up to 2K - 3 bytes
Information Field
Information Field
DATA
DATA