Datasheet

DS26521 Single T1/E1/J1 Transceiver
72 of 258
Figure 8-19. E1 Transmit Pulse Templates
0
-0.1
-0.2
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
1.1
1.2
0
TIME (ns)
SCALED AMPLITUDE
50 100 150 200 250-50-100-150-200-250
269ns
194ns
219ns
(in 75 ohm systems, 1.0 on the scale = 2.37Vpeak
in 120 ohm systems, 1.0 on the scale = 3.00Vpeak)
G.703
Template
8.11.2.2 Transmit Power-Down
The individual transmitters can be powered down by setting the TPDE bit in the LIU Maintenance Control register
(
LMCR). Note that powering down the transmit LIU results in a high-impedance state for the corresponding TTIP
and TRING pins.
When tansmit all ones (AIS) is invoked, continuous ones are transmitted using MCLK as the timing reference. Data
input from the framer is ignored. AIS can be sent by setting a bit in the
LMCR. Transmit all ones will also be sent if
the corresponding receiver goes into LOS state and the ATAIS bit is set in the
LMCR.
8.11.2.3 Transmit Short-Circuit Detector/Limiter
Each transmitter has an automatic short-circuit current limiter that activates when the load resistance is
approximately 25Ω or less. SCS (
LRSR.2) provides a real-time indication of when the current limiter is activated.
The LIU Latched Status register (
LLSR) provides latched versions of the information, which can be used to activate
an interrupt when enable via the
LSIMR register.
8.11.2.4 Transmit Open-Circuit Detector
The DS26521 can also detect when the TTIP or TRING outputs are open circuited. OCS (
LRSR.1) provides a real-
time indication of when an open circuit is detected. Register
LLSR provides latched versions of the information,
which can be used to activate an interrupt when enabled via the
LSIMR register. The open-circuit detect feature is
not available in T1 CSU operating modes (LBO5, LBO6, and LBO7).