Switch SW2: CAS Multiframe
CAS multiframe uses Timeslot 16 (TS16) to send multiframe (MF)
alignment data. In CAS MF, a multiframe is defined as 16 frames,
where a frame consists of 32 64kb/s timeslots, numbered 0 to 31.
TS16 of the first frame in the MF contains the CAS MF alignment word
in the upper four bits. The alignment word is always 0000 (binary). The
2715RC does not perform any signaling in TS16 other than to insert
the MF alignment word, in order to maintain MF alignment. When CAS
MF is disabled, the unit transmits user data in TS16; therefore, up to 31
channels are available for user data. When it is enabled, TS16 is not
available to the user. In this case, the user can use up to 30 channels
for data. CAS MF can be used with CRC-4 MF or by itself. When en-
nabled, both units must employ CAS MF; if one unit is set for CAS MF,
and the other is not, the one using CAS MF will detect a loss of sync.
SW2
Option
Off
Disabled
On
Enable
Switch SW3 & SW4: CRC-4 Multiframe/External Clock Mode
In framed mode, SW3 is used for CRC-4 MF. CRC-4 Multiframe
uses Time Slot zero to carry CRC-4 information. It operates independ-
ently of CAS MF. When CRC-4 is enabled, the unit monitors the incom-
ing data stream for CRC-4 errors. It transmits CRC-4 error counts to
the transmitting unit. Excessive errors may cause loss of frame or loss
of sync. If CRC-4 MF is used, both units must be set for set for CRC-4
MF. Otherwise, the one using CRC-4 MF will detect loss of sync.
In unframed mode, SW3 is used along with SW4 to determine
the clock mode. In unframed mode, the model 2715RC can be set to
Network, internal, or external clock mode.
In framed mode SW4 is used alone to determine the 2715RC
transmitter timing. In framed mode, the Model 2715RC can be set to
Network or Internal Clock Mode.
The following charts represent both cases.
CLOCK MODES
Network Clock
Transmitter timing is derived from the received line
signal.
Internal Clock
Transmitter clock is derived from an internal source
clock.
External Clock
Transmitter timing is derived from the local DTE
device.
Note:
When using the 2715RC as a high-speed short range modem,
one unit of the link must be configured in either internal or external
clock, and the other end must be configured for network clock mode.
Switches SW5, SW6, SW7, and SW8
Use Switches SW5, SW6, SW7, and SW8 to set the DTE data rate.
SW5 SW6 SW7
SW8
Speed
Off
Off
Off
Off
Clear Channel (2.048Mbps)
1
On
Off
Off
Off
64kbps
Off
On
Off
Off
128kbps
On
On
Off
Off
192kbps
Off
Off
On
Off
256kbps
On
Off
On
Off
384kbps
Off
On
On
Off
512kbps
On
On
On
Off
640kbps
Off
Off
Off
On
768kbps
On
Off
Off
On
1024kbps
Off
On
Off
On
1280kbps
On
On
Off
On
1536kbps
Off
Off
On
On
1600kbps
On
Off
On
On
1920kbps
Off
On
On
On
1984kbps
2
On
On
On
On
Invalid
8
7
UNFRAMED (G.703)
SW3
SW4
Clock Mode
Off
Off
Network (Default)
Off
On
Internal
On
On
External
On
Off
Network
MULTIFRAME(G.704)
SW3
CRC-4 MF
SW4
Clock Mode
On
On
Off
Network
Off
Off
On
Internal
