cx28380 Mindspeed Technologies, cx28380 Datasheet - Page 31

• Manufacturer Part Number: cx28380
• Description: Cn8380 Quad T1/e1 Line Interface
• Manufacturer: Mindspeed Technologies

Table 2-3.
In Hardware Mode, standard pulse templates are selected globally for all channels using hardware pins PTS(2:0).
See
In Host Mode, standard pulse templates are selected per channel by writing to register bits PULSE(2:0) [TLIU_CR;
addr n2]. If desired, custom pulse shapes can be programmed for each channel using the SHAPEn [addr n8 – nF]
registers and the PPT [TLIU_CR; addr n2] register bit. The data written into the SHAPEn registers is 5-bit
magnitude only. The first four code values of the pulse define the first half of the symbol, and the last four values
define the last half of the symbol. The last half symbol polarity is always forced to be opposite from the first half
polarity.
Figure 2-7.
2.4.6
The transmit DAC converts digitally shaped AMI pulses into analog bipolar signals. The line driver provides a high
impedance, current drive for the transmit DAC and outputs transmit signals to the XTIP[n] and XRING[n] output
pins. The high impedance driver allows line impedance matching using external parallel resistors to meet return
loss requirements. In applications which require surge protection, pulse amplitude compensation is provided if
series protection resistors (line-feed resistors) are needed in series with XTIP[n] and XRING[n]. When a shorted
line is detected, transmit monitor and protection circuits reduce the output current level to less than 50 mA RMS.
The standard transmit transformer for the CX28380 has a turns ratio of 1:2 (chip-side:line-side). To minimize power
consumption, an alternate 1:1.36 turns ratio transformer can be used in an unterminated configuration.
2.4.6.1
Various transmitter termination options are available to meet almost any interface requirement.
illustrates the location of the transmit termination components. In this figure, Ct is a smoothing capacitor across
29380-DSH-001-B
ITU–T G.703
75 Ω Coaxial Cable
ITU–T G.703
120 Ω Twisted Pair
FCC Part 68 Opt A I.431
100 Ω Twisted Pair
Chapter
Figure 2-7
Application
1,
Transmit Pulse Configurations (2 of 2)
Transmit Pulse Shape
Table
Driver
Transmit Termination Options
illustrates the shaped transmit signals.
8380_011
1-1.
AMI Pulses
8 x TCLK
Digitized
TCLK
Preliminary Information / Mindspeed Proprietary and Confidential
Line Rate
E1
E1
T1
Mindspeed Technologies
Positive Pulse
Shape Data
Magnitude
(0x00–0x1F)
Line Length
—
—
—
®
Hardware Mode
Configuration
PTS(2:0)
Negative Pulse
101
110
111
Host Mode Configuration
Circuit Description
[TLIU_CR; addr n2]
Figure 2-8
PULSE(2:0)
101
110
111
23