m21330 Mindspeed Technologies, m21330 Datasheet - Page 22

• Manufacturer Part Number: m21330
• Description: 4.25 Gbps Quad-channel Cable Driver And Adaptive Equalizer With 4x4 Crosspoint Switch
• Manufacturer: Mindspeed Technologies

5.4
There is signal detect circuit that will assert an alarm if the signal level at the input of the device is lower than
approximately 100 mVppd. Once asserted, the alarm will remain asserted until the signal is above approximately
200 mVppd. There is hysteresis between the assert and de-assert levels to prevent chattering of the LOS alarm.
When the input voltage level is between 100 mVppd and 200 mVppd, the LOS alarm can be high or low. The LOS
circuit should be disabled when used with strings of 1010 data that last for more than approximately 3 us to avoid
false LOS alarms. By default, the xALARM hardware pin operates as an interrupt signal and will generate an
interrupt signal with a pulse width of approximately 350 ns when there is an alarm on any input channel. See
Figure 5-2
xALARM pin acts as a status indicator rather than an interrupt signal, register address 87h[3] can be used.
Figure 5-2.
5.5
Each input channel of the M21330 includes an input equalizer, designed to compensate for bandwidth limitations of
50Ω twinaxial cables. The equalizer can operate in the adaptive mode or in a manual mode, where a fixed
equalization setting is selected. In the adaptive equalization mode, the equalizer will select the optimal equalization
setting for the cable/backplane type and length connected to the input. The input equalization is configured through
register addresses 00h, 02h, 04h, and 05h.
5.6
Each output buffer of the M21330 includes a de-emphasis circuit that is manually configured by the user. There is
approximately 6 dB of de-emphasis available, and the de-emphasis levels are selectable. The output de-emphasis
is controlled through register addresses 06h, 07h, 08h, and 09h.
5.7
Some protocols, such as SATA/SAS and PCIe, define a third logic state at the common mode for transmission of an
electrical idle level. In SAS/SATA systems, OOB signals such as COMRESET, COMWAKE, and COMSAS utilize
burst and idle levels for communication. The M21330 is designed to pass the electrical idle (EI) through the device
to support SATA/SAS and PCIe protocol requirements. When the EI feature of the M21330 is enabled, the device
will detect and pass EI signals with minimal distortion of the signal. LOS should be set to "never squelch" when the
EI circuit is enabled to allow the device to detect data bursts quickly after electrical idle periods that last longer than
approximately 5 us. The EI feature is enabled/disabled through register address 01h, and is disabled by default.
Note: If the M21330 is used in a PCIe application that requires support of the L0s power management state,
contact your Mindspeed representative for details on using the device in this application.
21330-DSH-001-B
below for an example of the timing for the xALARM interrupt signal. To configure the device so that the
Timing of xAlarm Interrupt Signal
LOS Alarm
Input Equalization
Output De-emphasis
Electrical Idle Pass-through
DVDDIO
GND
Mindspeed Technologies
350 ns
®
Functional Description
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