ITU-X225

SPDU structure: fields

SPDU global structure

bits 8 _ _ _ _ _ _ 1 SPDU fields
1 octet SI: Spdu Identifier
1 or 3 octets LI: Length Indicator (of parameter field)
m octets Parameter field possibly including PGI and PI units
n octets User information field

PGI unit

bits 8 _ _ _ _ _ _ 1 PGI fields
1 octet PGI: Parameter Group Identifier
1 or 3 octets LI: Length Indicator (of parameter field)
m octets Parameters field possibly including PI units

PI unit

bits 8 _ _ _ _ _ _ 1 PI fields
1 octet PI: Parameter Identifier
1 or 3 octets LI: Length Indicator (of parameter field)
m octets Parameters field

LI field

LI fields indicating lengths within the range 0-254 shall comprise one octet.

LI fields indicating lengths within the range 255-65535 shall comprise three octets. The first octet shall be coded 11111111 (= FF H) and the second and third octets shall contain the length of the associated parameter field with the high order bits in the first of these two octets.

SPDU structure: list of types

Category 0 Category 2
GT Give Token DT Data Transfer
PT Please Token MIP Minor Sync Point
MIA Minor Sync Ack
Category 1 MAP Major Sync Point
CN Connect MAA Major Sync Ack
AC Accept RS Resynchronize
RF Refuse RA Resynchronize Ack
FN Finish AS Activity Start
DN Disconnect AR Activity Resume
NF Not Finished AE Activity End
AB Abort AEA Activity End Ack
AA Abort Accept AD Activity Discard
GTC Give Token Confirm ADA Activity Discard Ack
GTA Give Token Ack AI Activity Interrupt
EX Expedited Data AIA Activity Interrupt Ack
PR Prepare CD Capability Data
TD Typed Data CDA Capability Data Ack
CDO Connect Data Overflow ER Exception Report
OA Overflow Accept ED Exception Data
 

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updated:  27-Feb-04