The read eye centering algorithm is performed in parallel for all byte lanes and requires write and read access to memory. The goal of the PHY read eye centering algorithm is to center the strobe within the data eye in each byte in the read path. An initial pattern is written into memory, read back, and then evaluated. Then read DQS/DQS# is moved to find the left and right edges of the read eye, and the optimal position is calculated. After centering, another read is executed to confirm data integrity.
Read eye centering completion is signaled by the PGSR0.REDONE bit. The high-level error flag is PGSR0.REERR. Additional debugging information is listed in Table: DATX8 General Status Register 2 (DXnGSR2) and Table: DATX8 General Status Register 2 (DXnGSR2).
Table 17-28: DATX8 General Status Register 2 (DXnGSR2)
|
Register
|
Bits
|
Name
|
Description
|
Address
|
|
DX0GSR2
|
[4]
|
REERR
|
Read eye centering error: if set, indicates that the DATX8 has encountered an error during execution of the read eye centering training of byte 0.
|
FD0807E8
|
|
DX1GSR2
|
[4]
|
REERR
|
Same as above, for byte 1.
|
FD0808E8
|
|
DX2GSR2
|
[4]
|
REERR
|
Same as above, for byte 2.
|
FD0809E8
|
|
DX3GSR2
|
[4]
|
REERR
|
Same as above, for byte 3.
|
FD080AE8
|
|
DX4GSR2
|
[4]
|
REERR
|
Same as above, for byte 4.
|
FD080BE8
|
|
DX5GSR2
|
[4]
|
REERR
|
Same as above, for byte 5.
|
FD080CE8
|
|
DX6GSR2
|
[4]
|
REERR
|
Same as above, for byte 6.
|
FD080DE8
|
|
DX7GSR2
|
[4]
|
REERR
|
Same as above, for byte 7.
|
FD080EE8
|
|
DX8GSR2
|
[4]
|
REERR
|
Same as above, for byte 8.
|
FD080FE8
|
|
DX0GSR2
|
[5]
|
REWN
|
Read eye centering warning: if set, indicates that the DATX8 has encountered a warning during execution of the read eye centering training of byte 0.
|
FD0807E8
|
|
DX1GSR2
|
[5]
|
REWN
|
Same as above, for byte 1.
|
FD0808E8
|
|
DX2GSR2
|
[5]
|
REWN
|
Same as above, for byte 2.
|
FD0809E8
|
|
DX3GSR2
|
[5]
|
REWN
|
Same as above, for byte 3.
|
FD080AE8
|
|
DX4GSR2
|
[5]
|
REWN
|
Same as above, for byte 4.
|
FD080BE8
|
|
DX5GSR2
|
[5]
|
REWN
|
Same as above, for byte 5.
|
FD080CE8
|
|
DX6GSR2
|
[5]
|
REWN
|
Same as above, for byte 6.
|
FD080DE8
|
|
DX7GSR2
|
[5]
|
REWN
|
Same as above, for byte 7.
|
FD080EE8
|
|
DX8GSR2
|
[5]
|
REWN
|
Same as above, for byte 8.
|
FD080FE8
|
|
DX0GSR2
|
[11:8]
|
ESTAT
|
Error status: If an error occurred for byte 0 as indicated by REERR, the error status code can provide additional information regarding when the error occurred during the algorithm execution.
|
FD0807E8
|
|
DX1GSR2
|
[11:8]
|
ESTAT
|
Same as above, for byte 1.
|
FD0808E8
|
|
DX2GSR2
|
[11:8]
|
ESTAT
|
Same as above, for byte 2.
|
FD0809E8
|
|
DX3GSR2
|
[11:8]
|
ESTAT
|
Same as above, for byte 3.
|
FD080AE8
|
|
DX4GSR2
|
[11:8]
|
ESTAT
|
Same as above, for byte 4.
|
FD080BE8
|
|
DX5GSR2
|
[11:8]
|
ESTAT
|
Same as above, for byte 5.
|
FD080CE8
|
|
DX6GSR2
|
[11:8]
|
ESTAT
|
Same as above, for byte 6.
|
FD080DE8
|
|
DX7GSR2
|
[11:8]
|
ESTAT
|
Same as above, for byte 7.
|
FD080EE8
|
|
DX8GSR2
|
[11:8]
|
ESTAT
|
Same as above, for byte 8.
|
FD080FE8
|
Table 17-29: Read Eye Centering Error Indications
|
PGSR0.REERR
|
DXnGSR2.REERR
|
DXnGSR2.ESTAT
|
PGSR0.
REDONE
|
Error Condition
|
|
1
|
1
|
0000
|
1
|
Initial read data miscompare before centering.
|
|
1
|
1
|
0101
|
1
|
Read data miscompare after read eye centering.
|
The results of the read eye centering can be viewed in the DXnLCDLR3 and DXnLCDLR4 registers, as listed in Table: Read Eye Centering Results Registers.
Table 17-30: Read Eye Centering Results Registers
|
Register
|
Bits
|
Name
|
Description
|
Address
|
|
DXnLCDLR3
|
[8:0]
|
RDQSD
|
Read DQS delay: delay select for the read DQS (RDAS) LCDL for each byte.
|
FD08078C, FD08088C, FD08098C, FD080A8C, FD080B8C, FD080C8C, FD080D8C, FD080E8C, FD080F8C
|
|
DXnLCDLR4
|
[8:0]
|
RDQSND
|
Read DQSN delay: delay select for the read DQSN (RDQSN) LCDL for each byte.
|
FD080790, FD080890, FD080990, FD080A90, FD080B90, FD080C90, FD080D90, FD080E90, FD080F90
|