PEF2091 Siemens Semiconductor Group, PEF2091 Datasheet - Page 77

• Manufacturer Part Number: PEF2091
• Description: ICs for Communications(ISDN Echocancellation Circuit)
• Manufacturer: Siemens Semiconductor Group

The first four bits of this two byte message gives the address of the Monitor message.
This address defines the type of the Monitor message.
Example: A Monitor message with an address ’0
MON-0 message. A Monitor message with an address ’8
called MON-8 message.
The IEC-Q will respond only to MON-0, MON-1, MON-2 and MON-8 messages in the
active channel. All other messages will be ignored.
The 12 Bits D0-D11 of a Monitor message will have different meanings, depending on
message type and on the function used. An overview of Monitor Channel commands and
indications of the IEC-Q are listed in section 6.2, page 226.
Priority
In the receive direction Monitor Channel commands (given to the IEC-Q) will be handled
sequentially.
In the transmit direction messages will be handled according to the following priority if
several of them are pending (to be issued by the IEC-Q):
MON-0 will have the first priority and will be therefore issued first. MON-1 will have the
second, MON-2 the third and MON-8 the last priority. However, an already running
message will not be aborted, even if a higher priority message is pending.
Verification
The monitor message on DIN is considered valid only if it consists of exactly two bytes.
Longer messages or single-byte messages will be discarded.
A double last-look criterion is implemented for both bytes of the monitor message. If the
received bytes are not identical in the first two received frames the message will be
aborted.
Handshake Procedure
Figure 28 illustrates a Monitor Channel transfer of a 2-byte monitor command followed
by a 2-byte IEC-Q-response. This requires a minimum of 15 IOM
7 frames + transmission 8 frames = 1.875 ms). In case the controller is able to confirm
the receipt of first IEC-Q-response byte in the frame immediately following the
MX-transition on DOUT from high to low (i.e. in frame No. 9), 1 byte may be saved
frames + 7 frames).
Note 16: Transmission and reception of monitor messages can be performed
1) This is referred to as the "fast handshake"
Semiconductor Group
simultaneously by the IEC-Q. In the procedure depicted in figure 28 it would
be possible for the IEC-Q to transmit monitor data in frames 1–5 (excluding
EOM-indication) and receive monitor data from frame 8 onwards.
77
H
’, i.e. Address= ’0000’ will be called
H
’, i.e. Address= ’1000’ will be
Functional Description
®
-2 frames (reception
Data Sheet 01.99
PEB 2091
PEF 2091
1)
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