MC68181 Datasheet, PDF (36/119 Pages) Freescale Semiconductor, Inc – Advance Information ROAMING FLEX chip SIGNAL PROCESSOR

MC68181
Freescale Semiconductor, Inc.
FLEX Message Word Definitions
Symbol
K
N
R
S
Table A-3 Numeric Message Bit Definitions
Definition
6-bit Message Check Character (First 4 bits are in the vector word)—This check
character is calculated by initializing the message check character (K) to 0 and
summing the information bits of each code word in the message, (including control
information and termination characters and bits in the last message word) to a check
sum register. The information bits of each word are broken into three groups: the first
is the 8 bits comprising i₀ through i₇, the second group comprises bits i₈ through i₁₅,
and the third group comprises bits i₁₆ through i₂₀. Bits i₀, i₈, and i₁₆ are the LSBs of
each group. The binary sum is calculated, and the result is shortened to the eight
Least Significant Bits. The two Most Significant Bits are shifted 6 bits to the right and
summed with the six Least Significant Bits to form a new sum. This resultant sum is
one's complemented with the six LSBs of the result being transmitted as the message
check character.
Message Number—When the system supports message retrieval, the system
controller assigns message numbers (for each paging address separately) starting at
zero and progressing up to a maximum of sixty-three in consecutive order. The actual
maximum roll over number is defined in the pager code plug to accommodate values
set in the system infrastructure. When message numbers are not received in order,
the subscriber should assume a message has been missed. The subscriber or the pager
may determine the missing message number(s) allowing a request to be made for
retrieval. When a normal unnumbered numeric message is received (Message
Retrieval Flag = 0), it is not to be included in the missed message calculation.
Message Retrieval Flag—When this bit is set to 1, the pager expects to see messages
numbered in order (each address numbered separately). Detection of a missing
number indicates a missed message. A message received with R = 0 is allowed to be
out of order and shall not cause the pager to indicate that a message has been missed.
Special Format—In the numbered message format, this bit set to 1 indicates that a
special display format should be used.
MESSAGE FILL RULES
For numeric messages of thirty-six characters or less (thirty-four characters if
numbered), fewer than eight code words on the channel are required. Only code
words containing the numeric message are to be transmitted. The space character
($C) should be used to fill any unused 4-bit characters in the last word and zeros to
fill any remaining partial characters. The check sum is correspondingly shortened to
include only the code words comprising the shortened message along with the space
and fill characters used to fill in the last word.
SPECIAL FORMAT NUMERIC
Spaces and dashes as specified by the host are inserted into the received message.
This feature in certain markets saves the transmission of an additional word on the
channel. As an example, in the U.S. market a 10-character string (area code plus
telephone number) fits into two message words; if the dashes or parentheses are to be
A-8
MC68181 Technical Data Sheet
MOTOROLA
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