ZHCSGZ9G October 2017 – November 2022 TUSB564
PRODUCTION DATA
The TUSB564 supports up to 4 DisplayPort lanes at datarates up to 8.1Gbps (HBR3). The TUSB564, when configured in DisplayPort mode, monitors the native AUX traffic as it traverses between DisplayPort source and DisplayPort sink. For the purposes of reducing power, the TUSB564 manages the number of active DisplayPort lanes based on the content of the AUX transactions. The TUSB564 snoops native AUX writes to DisplayPort sink’s DPCD registers 0x00101 (LANE_COUNT_SET) and 0x00600 (SET_POWER_STATE). TUSB564disables/enables lanes based on value written to LANE_COUNT_SET. The TUSB564 disables all lanes when SET_POWER_STATE is in the D3. Otherwise, active lanes are based on value of LANE_COUNT_SET.
DisplayPort AUX snooping is enabled by default but can be disabled by changing the AUX_SNOOP_DISABLE register. Once AUX snoop is disabled, management of TUSB564 DisplayPort lanes are controlled through various configuration registers.
AUX snooping feature is only supported when TUSB564 is configured for I2C mode. When TUSB564 is configured for GPIO mode, the AUX snoop feature is disabled and all four DP lanes are enabled if HPDIN is asserted high.
When TUSB564’s AUX snoop feature is enabled, the syncs defined by the DisplayPort standard must be received in order for AUX snoop feature to function properly. AUX writes to panel’s DPCD address 0x00600 and 0x00101 should result in SET_POWER_STATE and LANE_COUNT_SET fields at TUSB564’s offset 0x12 to get set to the appropriate value. If these fields do not get set correctly, then incoming AUX may not be compliant. If this is the case, then it is best to disable AUX snoop by setting the AUX_SNOOP_DISABLE field at offset 0x13.