Texas Instruments DS320PR810-RSC-EVM, Руководство пользователя, Страница: 7 / 32

2.5 DS320PR810 RX Detect State Machine
Each DS320PR810 deploys an RX Detect state machine that governs the RX detection cycle as defined in the
PCI Express specification. At power up or after a manually triggered event, the redriver determines whether
or not a valid PCI Express termination is present at the far end of the link. The RX_DET pin of DS320PR810
provides additional flexibility to system designers to appropriately set the device in their desired mode, according
to
Table 2-5 .
Table 2-5. Four-Level Control Pin Settings
PD0 PIN LEVEL PD1 PIN LEVEL
RX_DET PIN
LEVEL
Channels
0-3 RXCommon-
mode Impedance
Channels
4-7 RXCommon-
mode Impedance
DESCRIPTION
L L L0 Always 50 Ω Always 50 Ω
PCI Express RX detection state
machine is disabled. Recommended
for non-PCI Express use cases.
L L L1
Pre Detect: Hi-Z
Post Detect: 50 Ω
Pre Detect: Hi-Z
Post Detect: 50 Ω
Outputs poll until 3 consecutive valid
detections.
L L L2
Pre Detect: Hi-Z
Post Detect: 50 Ω
Pre Detect: Hi-Z
Post Detect: 50 Ω
Outputs poll until 2 consecutive valid
detections.
L L L3 N/A N/A Reserved
L L L4(Float)
Pre Detect: Hi-Z
Post Detect: 50 Ω
Pre Detect: Hi-Z
Post Detect: 50 Ω
TX polls every ~150us until valid
termination is detected. Reset by
asserting PD0/1 high for 200us then
low.
H L X Hi-Z Pre Detect: Hi-Z
Post Detect: 50 Ω
Reset Channels 0-3 signal path.
L H X Pre Detect: Hi-Z
Post Detect: 50 Ω
Hi-Z Reset Channels 4-7 signal path.
H H X Hi-Z Hi-Z Reset all channels.
2.6 DS320PR810 DC Gain Control
When operating in Pin Mode, the GAIN pins can be used to set the overall data path DC (low frequency) gain of
the DS320PR810 as shown in
Table 2-6 .
Table 2-6. GAIN Control
GAIN/SDA PIN
LEVEL
GAIN SETTING
L0 –6 dB
L1 –4 dB
L2 -2 dB
L3 +2 dB
L4 (Float) 0dB (Recommended for most use cases)
The DC gain of each channel of each device can also be set by writing to SMBus, I2C registers in Slave or
Master Modes. Refer to the
DS320PR810 Programming Guide
www.ti.com Description
SNLU297 – MAY 2021
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DS320PR810-RSC-EVM User's Guide 7
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