MC145572PB Freescale Semiconductor, MC145572PB Datasheet - Page 111

• Manufacturer Part Number: MC145572PB
• Manufacturer: Freescale Semiconductor

Specifications of MC145572PB

• Number Of Line Interfaces: 1
• Control Interface: HDLC
• Lead Free Status / Rohs Status: Not Compliant

Freescale Semiconductor, Inc.
6
MCU MODE ACTIVATION AND DEACTIVATION
6.1
INTRODUCTION
This chapter describes the activation and deactivation procedure for the MC145572. It is assumed
that MC145572 is configured for the IDL2 mode of operation. The material covered in this chapter
is useful for all applications. It is strongly recommended that this chapter be read when the GCI mode
operation is to be used. Chapter 8 gives a detailed functional description of the GCI mode operation
including the activation and deactivation time flow diagrams.
Activation or start–up is the process U–interface transceivers use to initiate a robust full–duplex com-
munications channel. This process, which may be initiated from either the LT or NT mode U–interface
transceiver, is a well–defined sequence of procedures during which the training of the equalizers and
echo cancellers at each end of the transmission line takes place. Two types of activation, cold start
or warm start, may occur. The MC145572 is capable of automatically supporting both types.
Deactivation is the process used to gracefully end communication between the U–interface trans-
ceivers at each end of the transmission line. Only the LT mode U–interface transceiver may initiate
a deactivation procedure.
ANSI T1.601–1992 defines ten activation signals, described in Tables 6–1 and 6–2, for the U–interface
transceivers to use during the activation procedure. For instance, six basic frames of signal TN are
transmitted by the NT when it wants to wake up the LT or in response to the LT transmitting TL. Two
basic frames of signal TL are transmitted by the LT when it wants to wake up the NT. When the NT
is in the fully operational mode, it transmits the signal known as SN3 and receives SL3 from the LT
end. Conversely, when the LT is in fully operational mode, it transmits SL3 and receives SN3. Only
when the U–interface is fully activated, with the NT transmitting signal SN3 and the LT transmitting
SL3, are the 2B+D channels of data capable of being transmitted over the U–interface.
ANSI T1.601–1992 defines the M4 channel act bit, see BR0(b7) and BR1(b7), which signals the
far–end U–interface transceiver that the near–end is capable of transparently passing 2B+D data.
Figure 6–1 shows the activation diagram from the ANSI T1.601 specification. This figure can be used
in conjunction with this text to understand the activation sequence.
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MC145572
6–1
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