IMPORTANT: This section outlines advanced features of the PS-GTR transceiver. AMD strongly advices using the default settings in the PCW.
The PS-GTR transceiver TX driver is a high-speed voltage-mode differential output buffer. To maximize signal integrity, it includes the following features.
•Differential voltage control
•Transmit de-emphasis control
Each controller modifies the differential output voltage and de-emphasis to default values based on the protocol selected. Table: Default Differential Output Voltage and De-Emphasis by Protocol shows these default values on a per protocol basis.
Note: AMD recommends using the default TX differential output voltages and de-emphasis settings.
Table 29-3: Default Differential Output Voltage and De-Emphasis by Protocol
Protocol
|
Default Differential Output Voltage (Lx_TX_ANA_TM_16)
|
Default De-Emphasis (Lx_TX_ANA_TM_18)
|
USB3
|
850 mV
|
–3.5 dB
|
PCIe Gen. 1
|
850 mV
|
–3.5 dB
|
PCIe Gen. 2
|
850 mV
|
–3.5 dB (default) controller might modify this value to –6 dB during link-up.
|
GEM SGMII or 1000BASE-SX/LX
|
850 mV
|
0 dB
|
DisplayPort RBR, HBR, and HBR2
|
Controller modifies value during link-up.
|
Controller modifies value during link-up.
|
SATA Gen. 1, 2, and 3
|
425 mV
|
0 dB
|
Table: TX Configurable Driver Attributes defines the TX configurable driver attributes.
Table 29-4: TX Configurable Driver Attributes
Register name
|
Address offset
|
Bit
|
Value and description
|
TX Swing
|
L0_TX_ANA_TM_15
L1_TX_ANA_TM_15
L2_TX_ANA_TM_15
L3_TX_ANA_TM_15
|
Lane 0: 0x0003C
Lane 1: 0x0403C
Lane 2: 0x0803C
Lane 3: 0x0C03C
|
6
|
Enable TX full/low swing setting.
1'b0: Default set by the PCW.
1'b1: TX swing defined by L0_TX_ANA_TM_15[7], L1_TX_ANA_TM_15[7], L2_TX_ANA_TM_15[7], or L3_TX_ANA_TM_15[7].
|
7
|
1'b0: Full swing (>0.8V) – default value.
1'b1: Low swing (>0.4)
|
TX Margin
|
L0_TX_ANA_TM_16
L1_TX_ANA_TM_16
L2_TX_ANA_TM_16
L3_TX_ANA_TM_16
|
Lane 0: 0x00040
Lane 1: 0x04040
Lane 2: 0x08040
Lane 3: 0x0C040
|
0
|
Enable TX driver swing control.
1'b0: Default set by the PCW.
1'b1: TX differential output defined by L0_TX_ANA_TM_16[3:1], L1_TX_ANA_TM_16[3:1], L2_TX_ANA_TM_16[3:1], or L3_TX_ANA_TM_16[3:1].
|
3:1
|
If full swing:
000 ® 0.85V – default value.
001 ® 0.85V
010 ® 0.6375V
011 ® 0.53125V
100 ® 0.425V
101 ® 0.31875V
110 ® 0.2656V
111 ® 0.213V
If low swing:
000 ® 0.478V – default value.
001 ® 0.478V
010 ® 0.372V
011 ® 0.2656V
100 ® 0.159V
101 ® 0.10625V
110 ® 0.053V
111 ® Reserved
|
TX De-emphasis
|
L0_TX_ANA_TM_18
L1_TX_ANA_TM_18
L2_TX_ANA_TM_18
L3_TX_ANA_TM_18
|
Lane 0: 0x00048
Lane 1: 0x04048
Lane 2: 0x08048
Lane 3: 0x0C048
|
7:0
|
8'b0000_0000 ® –6.0 dB de-emphasis
8'b0000_0001 ® –3.5 dB de-emphasis
8'b0000_0010 ® –0.0 dB de-emphasis – default value.
Other settings not supported
1'b0: Default set by the PCW.
1'b1: TX de-emphasis value set by L0_TX_ANA_TM[7:0], L1_TX_ANA_TM[7:0], L2_TX_ANA_TM[7:0], or L3_TX_ANA_TM[7:0].
|
L0_TX_ANA_TM_118
L1_TX_ANA_TM_118
L2_TX_ANA_TM_118
L3_TX_ANA_TM_118
|
Lane 0: 0x001D8
Lane 1: 0x041D8
Lane 2: 0x081D8
Lane 3: 0xC1D8
|
0
|
Force TX swing de-emphasis
|