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3. Serial RapidIO Electrical Interface > Bit Error Rate Testing (BERT)
79
Tsi574 User Manual
June 6, 2016
Integrated Device Technology
www.idt.com
3.8.1
Digital Equipment Loopback
Digital equipment loopback is enabled on a per-port basis through the
and Clock Selection Register” on page 369
When this form of loopback is enabled, the serial port transmit logic is connected to the receive logic
just before the 8B/10B encoder and transmitter. Digital equipment loopback requires the use of packets
and a correctly configured lookup table. The Bit Error Rate Tester patterns cannot be used when in
Digital Equipment Loopback mode. The SerDes does not have to be trained or operational for this
loopback to function since the SerDes PHY is not included in the data path.
All incoming data for the port on its external link is ignored when digital equipment loopback is
enabled.
3.8.2
Logical Line Loopback
Logical line loopback causes a packet sent into the Tsi574’s internal switching fabric to be directed
back to the originating port. To cause packets to loop back in this fashion, configure the lookup tables
(LUTs) so the destination IDs are destined for the incoming port.
For more information on LUT programming, refer to
.
3.9
Bit Error Rate Testing (BERT)
The RapidIO ports on the Tsi574 have a built-in bit error rate test (BERT). This test is based either on
fixed symbols or on a pseudo-random bit sequence (PRBS). Each lane within a port has a pair of
Pattern Generators and Pattern Matchers.
3.9.1
BERT Pattern Generator
The BERT Pattern Generator can generate different patterns when the link is put into test mode.
shows what patterns are supported by programming the MODE bit in the
Generator Control Register” on page 391
.
BERT patterns are not framed RapidIO packets and, therefore, when running BERT testing in
Tsi574 the word alignment has to be turned off. This can be completed by de-asserting
RX_ALIGN_EN bit for the corresponding lane (see
“SRIO MAC x SerDes Configuration
Table 8: Patterns Supported by Generator
MODE Setting
Description
0
Pattern Generator is disabled
1
15
th
order linear feedback shift register (LFSR) polynomial: x
15
+ x
14
+ 1
2
7
th
order LFSR polynomial: x
7
+ x
6
+ 1
3
Fixed 10-bit pattern from bottom of PAT0 field