MC68181 Datasheet, PDF (43/119 Pages) Freescale Semiconductor, Inc – Advance Information ROAMING FLEX chip SIGNAL PROCESSOR

Freescale Semiconductor, Inc.
MC68181
FLEX Message Word Definitions
ALPHANUMERIC MESSAGE RULES FOR SYMBOLIC CHARACTERS SETS
In the past, paging protocols have supported symbolic characters (e.g., Chinese,
Kanji, etc.) using a 7-bit ASCII protocol. When the FLEX Alphanumeric mode is used
to carry this same signaling format, special fragmenting rules are required to
maintain character boundaries, so performance is optimized under poor signal
conditions. The following rules allow character positions within a fragment to be
determined when prior fragments are missing.
ENHANCED FRAGMENTATION RULES
• The pager must recognize <NUL> characters only at the end of fragments
where they are used as fill characters. The pager must remove these characters
so that the displayed message is not affected. In all other positions the NUL
character must be considered a result of channel errors. (This provides a
method to end each fragment with a complete character and does not disrupt
the pager that is not capable of following all of the EF (Enhanced
Fragmenting) rules.)
• The last fragment is to be completed by filling unused character positions
with <ETX> characters or <NUL> characters. (Original FLEX alphanumeric
message definition (<ETX>) plus the new <NUL> requirement.) When the
message ends exactly in the last character position in the last BCH codeword,
no additional <ETX> is required.
• The U and V bits in the message header are available in all fragments
following the initial fragment to aid in decoding. In the first fragment, the
pager must assume the message starts in the default Character mode. For the
second and remaining fragments, the definition of the (U,V) field is as shown
in the following table.
Table A-10 U and V Field Definition
U₀ V₀
Definition
0
0 EF not supported in controller
0
1 Reserved (for a second alternate character mode)
1
0 Default Character Mode—start position 1
1
1 Alternate Character Mode—start position 1
When the EF field is 00, the pager decodes messages, allowing characters to be split
between fragments. When the U, V field is not 0, 0, each fragment starts on a
character boundary with the character mode defined by the above table.
SECURE MESSAGE
The following tables describe the bit format of the secure messages. The 7-bit
characters of the message are designated as lower case letters a, b, c, d, etc. Secure
messages can be sent as fragments. The service provider has the option of dividing
the message into several pieces and sending the separate pieces at any time within a
given time period.
MOTOROLA
MC68181 Technical Data Sheet
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