DS_S5T8702 Datasheet, PDF (51/62 Pages) Samsung semiconductor – FEEX ALPHANUMERIC DECODER II

FEEX^TM ALPHANUMERIC DECODER II
S5T8702
BUILDING A FRAGMENTED MESSAGE
The longest message which will fit into a frame is 84 code words total of message data. 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.
Additional fragments can be expected when the "continue bit" in the 1st Message Word is set. This causes the
pager to examine every following frame for an additional fragment until the last fragment with the continue bit
reset is found. The only requirement relating to the placement in time of the remaining fragments is that no more
than 32 frames (1 minute) or 128 frames (4 minutes) as indicated by the service provider may pass between
fragment receptions.
Each fragment contains a check sum character to detect errors in the fragment, a fragment number 0, 1, or 2 to
detect missing fragments, a message number to identify which message the fragment is a part, and the continue
bit which either indicates that more fragments are in queue or that the last fragment has been received.
The following describes the sequence of events between the Host and the S5T8702 required to handle a
fragmented message:
• The host will receive a vector indicating one of the following types:
V₂V₁V₀
000
101
110
Type
Secure
Alphanumeric
Hex / Binary
• The S5T8702 will increment the all frame mode counter inside the S5T8702 and begin to decode all of the
following frames.
• The host will receive the Message Packet(s) contained within that frame followed by a Status Packet. The
host must decide based on the Message Packet to return to normal decoding operation. If the message is
indicated as fragmented by the Message Continued Flag "C" being set in the Message Packet then the host
does not decrement the all frame mode counter at this time. The host decrements the counter if the Message
Continued Flag "C" is clear by writing the All Frame Mode Packet to the S5T8702 with the "DAF" bit = 1. If
no other fragments, temporary addresses are pending and the FAF bit is clear in the All Frame Mode
Register, then the S5T8702 returns to normal operation.
• The S5T8702 continues to decode all of the frames and passes any address information, vector information
and message information to the host followed by a status packet indicating the end of the frame. If the
message is indicated as fragmented by the Message Continued Flag "C" in the Message Packet then the
host remains in the receive mode expecting more information from the S5T8702.
• After the host receives the second and subsequent fragment with the Message Continued Flag "C" = 1, it
should decrement the all frame mode counter by sending an All Frame Mode Packet to the S5T8702 with the
"DAF" bit = 1. Alternatively, the host may choose to decrement the counter at the end of the entire message
by decrementing the counter once for each fragment received.
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