Functional Description
The termination of the transmission operation may be indicated either with:
– XPR interrupt, if a positive acknowledgement has been received,
– XMR interrupt, if a negative acknowledgement has been received, i.e. the transmitted
message must be repeated (XMR = Transmit Message Repeat),
– TIN interrupt, if no acknowledgement has been received at all after N2 times the expiration
of the time period t (TIN = Timer INterrupt, XPR interrupt is issued additionally).
1
Note: Prerequisite for sending I frames in the auto mode (XIF) is that the internal operational
mode of the timer has been selected in the MODE register (TMD bit = 1).
The transparent transmission of frames (XTF command) is possible in all message transfer
modes. The successful termination of a transparent transmission is indicated by an XPR
interrupt.
In all cases, collisions which occur on the S-bus (D channel) before the first XFIFO pool has
been completely transmitted and released are treated without µP interaction. The ISAC-S will
retransmit the frame automatically.
If a collision is detected after the first pool has been released, the ISAC-S aborts the frame and
requests the processor to repeat the frame with an XMR interrupt.
2.8.5
Documentation of the Auto Mode
The auto mode of the ICC and ISAC-S is only applicable for the states 7 and 8 of the LAPD
protocol. All other states (1 to 6) have to be performed in Non-Auto Mode (NAM). Therefore
this documentation gives an overview of how the device reacts in the states 7 and 8, which
reactions require software programming and which are done by the hardware itself, when
interrupts and status register contents are set or change. The necessary software actions are
also detailed in terms of command or mode register access.
The description is based on the SDL-diagrams of the ETSI TS 46-20 dated 1989.
The diagrams are only annotated by documentary signs or texts (mostly register descriptions)
and can therefore easily be interpreted by anyone familiar with the SDL description of LAPD.
All deviations that occur are specially marked and the impossible actions, paths etc. are
crossed out.
To get acquainted with this documentation, first read through the legend-description and the
additional general considerations, then start with the diagrams, referring to the legend and the
register description in the Technical Manual if necessary.
We hope you will profit from this documentation and use our software-saving auto mode.
Semiconductor Group
117
INFINEON [ Infineon ]
