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2 Troubleshooting the Application
The following sections approach the debug from a high level, attempting to start with application characteristics
that have a broad impact and then zeroing in on more focused aspects of the design.
2.1 Read and Check Register Values for Basic Health Check
Read the registers and verify the default values shown in the data sheet. Note that the initial values of some
registers can vary based on strap options.
The expected register values for PHY operation and link in 1000 Mbps with auto-negotiation enabled are shown
in
Table
2-1.
Register Address (h)
0x0004
0x0005
0x006E
0x006F
With the PHY linked in a given speed, use these values as a reference to identify any variance from the
expected operation.
Example: After powering and linking the PHY in 10 Mbps, register 0x0001 is read at hex value 7969. Noting the
difference in this value from the expected value of 796D, the equivalent binary values are used to identify which
bits are distinct. In this case, bit[2] is low, while the expected value is high. Referencing the data sheet register
map, bit[2] of register 0x0001 corresponds to link status. From this, it is known that the PHY is not linked.
SNLA246C – OCTOBER 2015 – REVISED APRIL 2024
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Table 2-1. DP83867 Register Value References
Register Value (h)
0x0000
0x0001
0x0003
(1)
(2)
0x0009
0x000A
0x0010
0x0011
0x0012
0x0013
0x0014
0x0015
0x0016
0x0017
0x0018
0x0019
0x001E
(3)
Based on strap resistors
(3)
Based on strap resistors
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0x1140
Auto-negotiation enable and
0x769D
0xA231
0x0061
DUT 10/100Mbps advertisement
0xC1E1
LP 10/100Mbps advertisement
0x0300
Compliance test mode;
DUT 1000Base speed
0x3C00
LP 1000Base speed
0x5048
Enable SGMII;
Enable Power-Saving Mode;
Manual MDI or MDIX
0xBF02
0x0000
Interrupt status
0x1C42
Interrupt status 2
0x29C7
Enable Speed optimization
0x0000
RX_ER counter
0x0000
Enable PRBS generator and
Enable Loopback
0x0040
0x6150
LED configuration
0x4444
LED configuration 2
0x0002
Enable Auto-MDIX
Strap status register
Strap status register2
Troubleshooting the Application
Comments
MII loopback;
disable
Link Status
PHY revision
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configuration
PHY Status
checker;
PRBS status
TDR register;
DP83867 Troubleshooting Guide
3
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