DS92LX1621 Datasheet, PDF (35/44 Pages) National Semiconductor (TI) – 10 - 50 MHz Channel Link III Serializer and Deserializer with Embedded Bi-Directional Control Channel

Note: AT-SPEED BIST is only available in the Camera mode
and not the Display mode.
The following diagram shows how to perform system AT
SPEED BIST:
FIGURE 30. AT-SPEED BIST System Flow Diagram
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Step 1: Place the Deserializer in BIST Mode.
Serializer and Deserializer power supply must be supplied.
Enable the AT SPEED BIST mode on the Deserializer by set-
ting the BISTEN pin High. The DS92LX1622 GPIO[1:0] pins
are used to select the PCLK frequency of the on-chip oscilla-
tor for the BIST test on high speed data path.
TABLE 3. BIST Oscillator Frequency Select
DES GPIO [1:0]
00
01
10
11
Oscillator Source
External PCLK
Internal
Internal
Internal
min (MHz)
10
typ (MHz)
50
25
12.5
max (MHz)
50
The Deserializer GPIO[1:0] set to 00 will bypass the on-chip
oscillator and an external oscillator to Serializer PCLK input
is required. This allows the user to operate BIST under dif-
ferent frequencies other than the predefined ranges.
Step 2: Enable AT SPEED BIST by placing the Serializer into
BIST mode.
The deserializer will communicate through the back-channel
to configure Serializer into BIST mode. Once the BIST mode
is set, the Serializer will initiate BIST transmission to the De-
serializer.
Wait 10 ms for Deserializer to acquire lock and then monitor
the LOCK pin transition from LOW to HIGH. At this point, AT
SPEED BIST is operational and the BIST process has begun.
The Serializer will start transfer of an internally generated
PRBS data pattern through the high speed serial link. This
pattern traverses across the interconnecting link to the De-
serializer. Check the status of the PASS pin; a HIGH indicates
a pass, a LOW indicates a fail. A fail will stay LOW for ½ a
clock cycle. If two or more bits fail in a row the PASS pin will
toggle ½ clock cycle HIGH and ½ clock cycle low. The user
can use the PASS pin to count the number of fails on the high
speed link. In addition, there is a defined SER and DES reg-
ister that will keep track of the accumulated error count. The
Serializer DS92LX1621 GPIO[0] pin will be assigned as a
PASS flag error indicator for the bi-directional control channel
link.
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