MC68181 Datasheet, PDF (44/119 Pages) Freescale Semiconductor, Inc – Advance Information ROAMING FLEX chip SIGNAL PROCESSOR

MC68181
Freescale Semiconductor, Inc.
FLEX Message Word Definitions
Table A-11 Vector type V = 000 All Fragments
Message
Word
i0 i1 i2 i3 i4 i5 i6 i7 i8 i9 i10 i11 i12 i13 i14 i15 i16 i17 i18 i19 i20
1st
K₀ K₁ K₂ K₃ K₄ K₅ K₆ K₇ K₈ K₉ C₀ F₀ F₁ N₀ N₁ N₂ N₃ N₄ N₅ s₀ s₁
2nd
a₀ a₁ a₂ a₃ a₄ a₅ a₆ b₀ b₁ b₂ b₃ b₄ b₅ b₆ c₀ c₁ c₂ c₃ c₄ c₅ c₆
3rd
d₀ d₁ d₂ d₃ d₄ d₅ d₆ e₀ e₁ e₂ e₃ e₄ e₅ e₆ f₀ f₁ f₂ f₃ f₄ f₅ f₆
4th
g₀ g₁ g₂ g₃ g₄ g₅ g₆ h₀ h₁ h₂ h₃ h₄ h₅ h₆ i₀ i₁ i₂ i₃ i₄ i₅ i₆
5th
j₀ j₁ j₂ j₃ j₄ j₅ j₆ k₀ k₁ k₂ k₃ k₄ k₅ k₆ l₀ l₁ l₂ l₃ l₄ l₅ l₆
...
nth
iiiiiiiiiiiiiiiiiiiii
Table A-12 Secure Message Bit Definitions
Symbol
Definition
K
10-bit Fragment Check Character—This check character is calculated by initializing
the fragment check character (K) to 0 and summing the information bits of each code
word in the message fragment (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, the one's complement of the sum is determined, and the ten LSBs of
the result is transmitted as the message check character.
C
1-bit Message Continued Flag—When set, the Message Continued Flag indicates
fragments of this message are to be expected in following frames. The longest message
that fits into a frame is 84 code words total. Three alpha characters per word yields a
maximum message of 252 characters in a frame, assuming no other traffic. Messages
longer than this value must be sent as several fragments.
F
2-bit Message Fragment Number—This is a modulo 3 message fragment number that
is incremented by 1 in successive message fragments. Initial fragments start at 11 and
increment 1 for each successive fragment. The 11 state (after the start fragment) is
skipped in this process to avoid confusion with an initial fragment of a non-continued
message. The final fragment is indicated by Message Continued Flag being cleared.
A-16
MC68181 Technical Data Sheet
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