MC68181 Datasheet, PDF (39/119 Pages) Freescale Semiconductor, Inc – Advance Information ROAMING FLEX chip SIGNAL PROCESSOR

Freescale Semiconductor, Inc.
MC68181
FLEX Message Word Definitions
Table A-6 Hex/Binary Message Bit Definitions (Continued)
Symbol¹
Definition
D
1-bit Display Direction Field—
• D = 0—Display left to right
• D = 1—Display right to left (valid only when data sent as characters (i.e.,
Blocking Length not equal 0001)).
H
1-bit Header Message—
• H = 1—Indicates that this message is a header to a following transparent
message of the same message number
• H = 0—Implies message is not a header
B
4-bit Blocking Length—This bit field indicates the number of bits per character.
• B₃B₂B₁B₀ = 0001—1 bit per character (binary/transparent data)
• B₃B₂B₁B₀ = 1111—15 bits per character
• B₃B₂B₁B₀ = 0000—16 bits per character
Data with blocking length other than 1 is assumed to be displayed on a character by
character basis. (default value = 0001)
s
5-bit Field Reserved for future use—Default value = 00000
S
8-bit Signature Field—The signature is defined to be the one's complement of the
binary sum over the total message taken 8 bits at a time prior to formatting into
fragments. It would be equivalent to a binary sum starting with the first 8 bits directly
following the signature field (b₃b₂b₁b₀a₃a₂a₁a₀ + d₃d₂d₁d₀c₃c₂c₁c₀ and so on) and
continuing all the way to the last valid data bit in the last word of the last fragment.
The 8 Least Significant Bits of the result are inverted (one's complement) and
transmitted as the message signature.²
Note:
1. Fields R through S are only in the first fragment of a message. The fields K through N make up
the first word of every fragment in a long message.
2. This sum does not include any termination bits and should be calculated directly on the message
as received by the terminal. The device generating the signature should be able to calculate
before the fragmenting boundaries are determined.
MESSAGE CONTENT
Starting with the first character of the third word in the message (second word in the
remaining fragments), each 4-bit field represents one of any of the sixteen possible
combinations with no restrictions (data may be binary).
FRAGMENT TERMINATION
Unused bits in the last message word of a fragment are filled with all 0s or all 1s,
depending on the last valid data bit. This choice is always the opposite polarity of the
last valid data bit. For first fragments and inner fragments of a multi-fragment
MOTOROLA
MC68181 Technical Data Sheet
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