DCE is used to clock data in both directions. If the cable is too long,
propagation delays may cause data received by the DCE to be out of
phase with the clock transmitted to the DTE. Thus, data may be
corrupted.
In terminal timing mode, data from the Access-T is clocked into the
DTE by a clock from the Access-T, and data from the DTE is clocked
into the Access-T by a clock from the DTE. In other words, each data
path has its own clock, transmitted in the same direction as the data
(as illustrated in Figure 2-2). This eliminates the problems created by
propagation delays when standard timing is used. Note, however,
that if there is no signal on External Clock from the DTE to the
Access-T, Access-T removes Receive Clock.
Terminal timing may not be enabled for a DTE port which is the
master clock source for the Access-T. For example,
TTM=YES
for Port
1 is not valid if
MASTER=PORT1
.
Note:
If no DTE is connected to a DTE port, ensure that
TTM=OFF
before initiating a local CS DTE or remote CS
Line loopback.
Both the Access-T and the DTE must be configured for the same
timing mode. Thus, terminal timing should be enabled at the Access-T
only if the DTE is configured to transmit in phase with External Clock
and to receive in phase with a Receive Clock.
Determine the timing mode. Move the cursor to
TTM
and specify
whether terminal timing mode is to be
ON
or
OFF
.
9.
Move the cursor to
BIT 7
and press the
Enter
key. If Bit 7 stuffing is to
be enabled, select
ON
. If Bit 7 stuffing is to be disabled, select
OFF
. (Bit 7
stuffing is recommended for voice channels when the rate is Nx64 and
minimum pulse density is not assured in any other way—e.g., B8ZS
encoding.) Press the
Esc
key.
Note:
Bit 7 stuffing and B8ZS coding cannot be enabled
at the same time.
10.
Press the
Esc
key repeatedly to return to the Main Menu Line.
ACST-0351-005
Chapter 6
June 1996
Configuration Procedures
6-13