MC68181 Datasheet, PDF (58/119 Pages) Freescale Semiconductor, Inc – Advance Information ROAMING FLEX chip SIGNAL PROCESSOR

MC68181
Freescale Semiconductor, Inc.
FLEX Message Word Definitions
Long CAPCODE 1,075,843,073 to 3,223,326,720
Long address sets 1–3 and 1–4 are in this range. The 1st word of the long address is
calculated following the same rules for the long addresses set 1–2. The second long
address word is determined by subtracting 2,068,481 from the CAPCODE, the
resultant number is divided by 32,768 with the integer portion added to 1,933,312.
This value is converted to a 21-bit binary number, which becomes the (31,21) BCH
code word transmitted over the air as the second address word.
Long CAPCODE 3,223,326,721 to 4,297,068,542
Long address set 2–3 is in this range. The first word is determined by subtracting
2,068,479 from the CAPCODE. The remainder of dividing by 32,768 is retained (i.e.,
modulo 32,768). This value is then added to 2,064,383 with the result converted to a
21-bit binary number, which becomes the information bits in the (31,21) BCH code
word transmitted over the air as the 1st address word.
The second word is determined by subtracting 2,068,479 from the CAPCODE and
finding the integer portion after dividing by 32,768. This value is then added to
1,867,776 and converted to a 21-bit binary number, which becomes the (31,21) BCH
code word transmitted over the air as the second address word.
BINARY TO CAPCODE CONVERSION
With the address code word values that are transmitted over the air, the CAPCODE
can be calculated by performing the inverse of the above-specified process. As an
example, the short address code word is converted to decimal and the number 32,768
is subtracted to arrive at the 7-digit address portion of the CAPCODE. For the two
word long address set 1–2, the address word 1 is first converted from binary to
decimal. The second address word is then complemented, (or subtracted from
2,097,151 decimal) and converted to a decimal. This value is multiplied by 32,768,
added to 2,068,480, and then added to address word 1. The result is the address
portion of the FLEX CAPCODE.
A-30
MC68181 Technical Data Sheet
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