mc68181 Freescale Semiconductor, Inc, mc68181 Datasheet - Page 42

• Manufacturer Part Number: mc68181
• Description: Signal Processor
• Manufacturer: Freescale Semiconductor, Inc

MC68181
FLEX Message Word Definitions
A-14
Symbol
MESSAGE CONTENT
MESSAGE TERMINATION
U, V
M
N
R
S
Starting with the second character of the second word in the message (1st character of
the second word in all remaining fragments), each 7-bit field represents Standard
ASCII (ISO 646-1983E) characters with options for certain International characters.
The ASCII character ETX (03) should be used to fill any unused 7-bit characters in a
word. In the case where symbolic characters are being transmitted, special rules for
fragment and message termination are defined in the following information on
Alphanumeric Message Rules for Symbolic Characters Sets.
Message Number—When the system supports message retrieval, the system controller
assigns message numbers (for each paging address separately) starting at 0 and
progressing up to a maximum of 63 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 is equal to 0),
it is not to be included in the missed message calculation. This number is also used to
identify fragments of the same message. Multiple messages to the same address must
have separate message numbers.
Message Retrieval Flag—When this bit is set, 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 not cause the pager to indicate that a message has been missed.
1-bit Mail drop Flag—When set, this flag indicates the message is to be stored in a
special area in memory. It automatically writes over existing data in that memory
space.
7-bit Signature Field—The signature is defined to be the one's complement of the
binary sum over the total message (all fragments) taken 7 bits at a time (on alpha
character boundary) starting with the first 7 bits directly following the signature field
(a6a5a4a3a2a1a0, b6b5b4b3b2b1b0, etc.). The seven Least Significant Bits of the result
are transmitted as the message signature.
Fragmentation control bits—This field exists in all fragments except the first fragment.
It is used to support character position tracking in each fragment when symbolic
characters (characters made up of 1, 2, or 3 ASCII characters) are transmitted using the
Alphanumeric message type. The default value for the U, V pair is 0, 0. See Enhanced
Fragmentation Rules on page A-15 for more information.
Table A-9 Alphanumeric Message Bit Definitions (Continued)
MC68181 Technical Data Sheet
Freescale Semiconductor, Inc.
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Definition
MOTOROLA