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RELEASED
PM4354 COMET-QUAD
DATASHEET
PMC-1990315
ISSUE 6
FOUR CHANNEL COMBINED E1/T1/J1
TRANSCEIVER / FRAMER
PROPRIETARY AND CONFIDENTIAL TO PMC-SIERRA, INC. AND FOR ITS CUSTOMERS’ INTERNAL USE
66
Jitter Generation
In the absence of input jitter, the output jitter shall be less than 0.025 UIpp. This complies with the
AT&T TR 62411 requirement of less than 0.025 UIpp of jitter generation.
9.30 Line Transmitter
The line transmitter generates Alternate Mark Inversion (AMI) transmit pulses suitable for use in
the DSX-1 (short haul T1), short haul E1, long haul T1 and long haul E1 environments. The
voltage pulses are produced by applying a current to a known termination (termination resistor
plus line impedance). The use of current (instead of a voltage driver) simplifies transmit Input
Return Loss (IRL), transmit short circuit protection (none needed) and transmit tri-stating.
The output pulse shape is synthesized digitally with current digital-to-analog (DAC) converters,
which produce 24 samples per symbol. The current DAC’s produce differential bipolar outputs
that directly drive the TXTIP1[x], TXTIP2[x] TXRING1[x], and TXRING2[x] pins. The current
output is applied to a terminating resistor and line-coupling transformer in a differential manner,
which when viewed from the line side of the transformer produce the output pulses at the required
levels and insures a small positive to negative pulse imbalance.
The pulse shape is user programmable. For T1 short haul, the cable length between the COMET-
QUAD and the cross-connect (where the pulse template specifications are given) greatly affects
the resulting pulse shapes. Hence, the data applied to the converter must account for different
cable lengths. For CEPT E1 applications the pulse template is specified at the transmitter, thus
only one setting is required. For T1 long haul with a LBO of 7.5 dB the previous bits effect what
the transmitter must drive to compensate for inter-symbol interference; for LBO’s of 15 dB or
22.5 dB the previous 3 or 4 bits effect what the transmitter must send out.
Refer to the Operation section for details on creating the synthesized pulse shape.
9.31 Timing Options (TOPS)
The Timing Options block provides a means of selecting the source of the internal input clock to
the TJAT block, and the reference clock for the TJAT digital PLL.
9.32 JTAG Test Access Port
The JTAG Test Access Port block provides JTAG support for boundary scan. The standard JTAG
EXTEST, SAMPLE, BYPASS, IDCODE and STCTEST instructions are supported.
9.33 Microprocessor Interface
The Microprocessor Interface Block provides normal and test mode registers, the interrupt logic,
and the logic required to connect to the Microprocessor Interface. The normal mode registers are