
APPENDIX
Protocol Data Mode
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19.01.2007
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5. Appendix
5.1
Protocol Data Mode
The protocol data mode is a sub-mode of the data mode. It allows multiplexed data
transmission using the RS-232 interface. The protocol data mode is selected by issuing the
configuration command SPPR ON.
Only the single bearer FT may operate in protocol data mode.
The protocol data mode allows the simultaneous handling of multiple connections at the FT.
Moreover it provides more flexibility than the transparent data mode.
Call control is handled by software through a dedicated command channel.
In order to use the protocol mode the host must format its data according to a specific
protocol which is described below.
5.1.1 General
Description
The HW 86012/22 implements data transmission according to the DECT standard DSP C.2
(EN 300 651). This standard uses the LU3 protocol, which consists in an error-protected
frame relay (LU2) together with a LAP (link access protocol).
LU2 provides an asynchronous frame-oriented data service.
The purposes of LAP are end-to-end link control, error correction and flow control. LAP
provides an asynchronous, stream-oriented interface to the upper layer. Data is transmitted
as an asynchronous sequence of frames.
In transparent data mode both layers of LU3, i.e. LU2 and LAP, are executed on the module.
The host interfaces to the upper interface of LAP. This is illustrated in this figure.
FT-side
host
FT
LAP
LU2
PT
LU2
LAP
PT-side
host
RS 232
RS 232
DECT
Figure 5: Distribution of LU3 in transparent data mode
In protocol data mode the FT may serve multiple connections. Each of them requires end-to-
end link control, error correction and flow control. Therefore in protocol mode the LU3 layer
is distributed between host and module. LAP is executed on the host and LU2 on the
module. This is illustrated in Figure 6. Please observe that in this example PT1 to PT4
operate in transparent data mode.