PEB20534H-10V2.1 Infineon Technologies, PEB20534H-10V2.1 Datasheet - Page 188

• Manufacturer Part Number: PEB20534H-10V2.1
• Description: Communication Controller 208-Pin FQFP
• Manufacturer: Infineon Technologies

8.1.9.7
When transporting bit-files (as opposed to text files), or compressed files, the characters
could easily represent MODEM control characters (such as CTRL-Q, CTRL-S) which the
MODEM would not pass through. The DSCC4 maintains an Async Control Character
Map (ACCM) for characters 00-1F Hex. Whenever there is a mapped character in the
data stream, the transmitter precedes that character with a control-escape character of
7D
character e.g. 13
At the receive end, a 7D
by inverting bit 5 (e.g. if 7D
changed to 13
In addition to the ACCM, 4 user programmable characters (especially outside the range
00-1F Hex) can also be mapped using the control-escape sequence described above.
These characters are specified in register UADC.
The receiver discards all characters which are received unmapped, but expected to be
mapped because of ACCM and UDAC register contents. If this occurs within an HDLC
frame, the unexpected characters are discarded before forwarded to the receive CRC
checking unit.
7D
The sequence of mapping control logic is:
1. 7D
2. ACCM,
3. UDAC.
The 32 lookup octet values (00
programmable register is used to select which of the 32 fixed characters have to be
mapped using the control-escape sequence. This is maintained by register ACCM.
Register UDAC provides the additional 4 user programmable characters to be mapped.
Data Sheet
H
H
. After the control-escape, the character itself is transmitted with bit 5 inverted.
(control-escape) and 7E
H
and 7E
Data Transparency in PPP Mode
H
H
the original character).
octets,
H
is mapped to 7D
H
character is discarded and the following character is modified
H
H
, 33
(flag) octets in the data stream are mapped in general.
H
H
H
-1F
, 33
is received, the 7D
H
) are stored within the device.
H
).
188
Detailed Protocol Description
H
is discarded and the 33
PEB 20534
PEF 20534
One dword
2000-05-30
H
is