XRT83SL28
xr
8-CHANNEL E1 SHORT-HAUL LINE INTERFACE UNIT
REV. 1.0.0
2.4
TAOS (Transmit All Ones)
The XRT83SL28 has the ability to transmit all ones on a per channel basis by programming the appropriate
channel register. If TAOS is enabled, the Transmitter outputs will generate an All Ones pattern regardless of
the Transmit Input data. The Remote Loop Back mode has priority over TAOS. Figure 15 is a diagram showing
the all ones signal at TTIP and TRING.
FIGURE 15. TAOS (TRANSMIT ALL ONES)ATAOS (AUTOMATIC TRANSMIT ALL ONES)
1
1
1
TAOS
2.5
ATAOS (Automatic Transmit All Ones)
Unlike TAOS, ATAOS is used to generate an All Ones signal only when an RLOS condition occurs. If ATAOS is
enabled, any channel that experiences an RLOS condition will automatically cause the transmitter on that
channel to send an all ones pattern to the line. When RLOS clears, the All Ones pattern ends and the Transmit
path returns to normal operation. For TAOS on the receive output pins, see ARAOS in the Receive Section of
this datasheet. A simplified block diagram of the ATAOS function is shown in Figure 16.
FIGURE 16. SIMPLIFIED BLOCK DIAGRAM OF THE ATAOS FUNCTION
TTIP
TRING
Tx
TAOS
ATAOS
RLOS
2.6
Transmitter Power down in Hardware mode
In Hardware mode, if TCLK is pulled "Low" for 16 MCLK cycles the transmitter outputs at TTIP/TRING are tri-
stated. If TCLK is pulled "High" for 16 MCLK cycles the transmitter will send an All Ones signal to the line,
using MCLK as reference.
2.7
DMO (Driver Monitor Output)
The driver monitor circuit is used to detect transmit driver failures by monitoring the activities at TTIP/TRING
outputs. Driver failure may be caused by a short circuit in the primary transformer or system problems at the
transmit inputs. If the transmitter of a channel has no output for more than 128 TCLK cycles, DMO goes "High"
until a valid transmit pulse is detected. If the DMO interrupt is enabled, the change in status of DMO will cause
the interrupt pin to go "Low". Once the status register is read, the interrupt pin will return "High" and the status
register will be reset (RUR).
22
EXAR [ EXAR CORPORATION ]
