YTD428_07 Datasheet, PDF (16/28 Pages) YAMAHA CORPORATION – IDSU ISDN DSU for Terminal Equipment

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DETAILS OF FUNCTIONS
4.3 Interface Switch Section
Normally, this section connects T I/F section with CT/LT section to provide DSU function (NTSEL = “H”).
By setting this section, the driver/receiver function of the T I/F section can be separated from the CT/LT
section and be used independently (NTSEL = “L”).
For example, it is useful under such a situation that there are some terminals which have DSU function on
the same S/T line.
RA / RB
TA / TB
T ref.
pt. I/F
YTD428
I/F
switch
CT
and
LT
U ref.
pt. I/F
DSU section
L1
L2
U ref. pt.
driver
TTL I/F
Call control
circuit
(No transformer is required)
YTD418 or
YTD423
Layer 3 information
(Bch data)
Figure 4.1 Image Of Using T Ref. Pt. I/F Drive/Receiver Independently
In case of using NTSEL = "L" (TE mode), the signals of TA/TB and RA/RB should be reversed by switches
or other devices. Because S/T bus signals that are connected to TA, TB, RA and RB pin are different between
using YTD428 as DSU (NTSEL = "H") and S/T terminal (NTSEL = "L").
Generally speaking, the terminal resistors are only mounted on the nearest terminal from DSU and other
terminals that are connected with the same bus don't require the terminal resistors. Therefore, it is useful that
switches which can control ON/OFF of the terminal resistors are provided on the equipment.