IDT82P2288
OCTAL T1/E1/J1 LONG HAUL / SHORT HAUL TRANSCEIVER
Functional Description
109
March 04, 2009
3.25 LINE DRIVER
The Line Driver can be set to High-Z for redundant application.
The following ways will set the drivers to High-Z:
- Setting the THZ pin to high will globally set all the Line Drivers to
High-Z;
- When there is no clock input on the OSCI pin, all the Line Drivers
will be High-Z (no clock means this: the input on the OSCI pin is
in high/low level, or the duty cycle is less than 30% or larger than
70%);
- After software reset, hardware reset or power on, all the Line
Drivers will be High-Z;
- Setting the T_HZ bit to ‘1’ will set the corresponding Line Driver
to High-Z;
- In Transmit Clock Master mode, if the XTS bit is ‘1’, the source of
the transmit clock is from the recovered clock from the line side.
When the recovered clock from the line side is lost, the Line
Driver in the corresponding link will be High-Z;
- In Transmit Clock Slave mode, if the XTS bit is ‘0’, the source of
the transmit clock is from the backplane timing clock. When the
backplane timing clock is lost (i.e., no transition for more than 72
T1/E1/J1 cycles), the Line Driver in the corresponding link will be
High-Z. However, there is an exception in this case. That is, if the
link is in Remote Loopback mode, the Line Driver will not be
High-Z.
- When the transmit path is power down, the Line Driver in the cor-
responding link will be High-Z.
By these ways, the TTIPn and TRINGn pins will enter into high
impedance state immediately.
Controlled by the DFM_ON bit, the output driver short-circuit protec-
tion can be enabled. The driver’s output current (peak to peak) is limited
to 110 mA typically. When the output current exceeds the limitation, the
transmit driver failure will be captured by the DF_S bit. Selected by the
DF_IES bit, a transition from ‘0’ to ‘1’ on the DF_S bit or any transition
from ‘0’ to ‘1’ or from ‘1’ to ‘0’ on the DF_S bit will set the DF_IS bit.
When the DF_IS bit is ‘1’, an interrupt on the INT pin will be reported if
enabled by the DF_IE bit.
3.26 TRANSMITTER IMPEDANCE MATCHING
In T1/J1 mode, the transmitter impedance matching can be realized
by using internal impedance matching circuit. 100
, 110 , 75 or
120
internal impedance matching circuit can be selected by the
T_TERM[1:0] bits. The external impedance circuitry is not supported in
T1/J1 mode.
In E1 mode, the transmitter impedance matching can be realized by
using internal impedance matching circuit or external impedance
matching circuit. When the T_TERM[2] bit is ‘0’, the internal impedance
matching circuit is enabled. 100
, 110 , 75 or 120 internal
impedance matching circuit can be selected by the T_TERM[1:0] bits.
When the T_TERM[2] bit is ‘1’, the internal impedance matching circuit
is disabled, and different external resistors should be used to realize
different impedance matching.
Figure 2 shows the appropriate components to connect with the
cable for one link.
Table 75 lists the recommended impedance matching
values for the transmitter.
3.27 TESTING AND DIAGNOSTIC FACILITIES
3.27.1 PRBS GENERATOR / DETECTOR
The PRBS Generator / Detector generates test pattern to either the
transmit or receive direction, and detects the pattern in the opposite
direction. The direction is determined by the PRBSDIR bit. The pattern
can be generated or detected in unframed mode, in 8-bit-based mode or
in 7-bit-based mode. This selection is made by the PRBSMODE[1:0]
bits. In unframed mode, all the data streams are extracted or replaced
and the per-channel/per-TS configuration in the TEST bit is ignored. In
8-bit-based mode or in 7-bit-based mode, the extracted or replaced
channel/timeslot is specified by the TEST bit. (In 7-bit-based mode, only
the higher 7 bits of the selected channel/timeslot are used for PRBS
test).
Table 75: Impedance Matching Value For The Transmitter
Cable
Configuration
Internal Termination
External Termination
T_TERM[2:0]
RT
T_TERM[2:0]
RT
75
(E1)
0 0 0
0
1 X X
9.4
120
(E1)
0 0 1
100
(T1)
0 1 0
-
110
(J1)
0 1 1
-
Bit
Register
Address (Hex)
T_HZ
Transmit Configuration 1
023, 123, 223, 323,
423, 523, 623, 723
DFM_ON
XTS
Transmit Timing Option
070, 170, 270, 370,
470, 570, 670, 770
DF_S
Line Status Register 0
036, 136, 236, 336,
436, 536, 636, 736
DF_IES
Interrupt Trigger Edges Select
035, 135, 235, 335,
435, 535, 635, 735
DF_IS
Interrupt Status 0
03A, 13A, 23A, 33A,
43A, 53A, 63A, 73A
DF_IE
Interrupt Enable Control 0
033, 133, 233, 333,
433, 533, 633, 733
T_TERM[2:0]
Transmit And Receive Termi-
nation Configuration
032, 132, 232, 332,
432, 532, 632, 732