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Protocols
Issue 4 May 2002 1-13 555-233-123
Protocol States
Table 1-4 summarizes the protocols used at various points in the data
transmission stream. See Figure 1-1 on page 1-10 .
NOTE:
ADU means Asynchronous Data Unit
PCM means Pulse Code Modulated
DMI means Digital Multiplexed Interface
Both the physical-layer protocol and the Digital Multiplexed Interface (DMI) mode
used in the connection are dependent upon the type of 8-bit code used at layer 2
between the DTE equipment and DCE equipment, as listed in
Table 1-5 and
Table 1-6 on page 1-14 .
Table 1-4. Protocol States for Data Communication
Transmis-
sion Type
Incoming
DTE to
DCE
OSI
Layer
Protocols DTE to
DCE
DCE to System
Port Inside System
Analog Modem 1 RS-232, RS-449,
or V.35 analog PCM
2 8- or 10-bit code voice-grade data voice-grade data
ADU 1 RS-232 ADU proprietary raw bits
2 asynchronous
8-bit code asynchronous
8-bit code DMI
Digital Data
Module 1 RS-232, RS-449,
or V.35 DCP or BRI raw bits
2 8-bit code DMI DMI
Digital
Signal
Level 1
(DS1) 1 any DS1 PCM or raw bits
2 8-bit code DMI or voice-
grade data DMI or voice- grade
data
Table 1-5. Physical-Layer Protocol Versus Character Code
Protocol Code
RS-232 Asynchronous 8-bit ASCII, and synchronous
RS-449 Asynchronous 8-bit ASCII, and synchronous
V.35 Synchronous