SN75DP120

SLLSE08 – OCTOBER 2009

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Table 1. Description of SN75DP120 Modes

MODE

CHARACTERISTICS

CONDITIONS

ShutDown

Least amount of power consumption (most circuitry turned off);

LP# is low

Mode

HPD_SRC reflects HPD_SINK state, all other outputs are high

impedance and all other inputs are ignored.

DPCD registers and logic are held reset to default values

Standby Mode

Low power consumption; main link inputs and outputs are disabled,

LP# is high;

AUX monitoring is enabled

D3 Power

Low power consumption; main link inputs and outputs disabled,

LP# is high;

Down Mode

AUX monitoring is enabled

AUX command requested DP sink to enter D3

power saving mode

Active Mode

Data transfer (normal operation);

LP# is high;

The device is either in TMDS mode (CAD_SINK=high) or DP mode

HPD_SINK is high

(CAD_SINK=low);

(e.g. sink interrupt request to source)

In DP mode, the AUX monitor is actively monitoring for link training,

Link Training has begun or completed

and the output signal swing, input equalization level and lane count

depend on the link training. At power-up all main link outputs are

disabled by default. AUX Link training is necessary to overwrite the

DPCD registers to enable main link outputs.

In TMDS mode, the output signal swing will be 600mVp-p, and

transactions on the AUX lines will be ignored.

Output Disable DPCD write commands on the AUX bus detected by the SN75DP120

EN is high

Mode

will also write to the local DP120 DPCD register. The local DPCD

DPCD register 101h or 103h entry is invalid

registers should always be written with valid entries. If register 101h or

103h is written with an invalid value, the SN75DP120 disables the

OUTx main link output signals, forcing the DP sink to issue an

interrupt. The DP source can now re-train the link using valid DPCD

register values. As soon as all DPCD registers contain a valid entry,

the SN75DP120 switches back into the appropriate mode of operation.

For a list of valid and invalid DPCD register entries refer to Table 3 and

the DP1.1a specification Table 2-52 and Table 3-12.

Table 2. Transition Between Operational Modes

MODE TRANSITION

USE CASE

TRANSITION SPECIFICS

Shutdown

→ Standby

Activate DP120

1. LP# transitions from low to high

2. Receiver enters Standby mode

3. AUX listener turns on and begins to monitor the AUX

lines

Standby

→ Active

Turn on main link (monitor plugged in)

1. HPD_SINK input asserts high

2. Main link outputs turn on

Active

→ D3

DP source requests temporary power down for

1. Receive D3 entry command on AUX

power savings

2. Main link inputs and outputs are disabled

3. AUX monitor remains active

D3

→ Active

Exit temporary power down

1. AUX channel receives D3 exit command or HPD_SINK

transitions from low to high

2. Enable main link

D3

→ Standby

Exit temporary power down

Active

→ Standby

turn off main link (monitor unplugged)

2. Main link inputs and outputs are disabled

Active/Standby

→

Turn off DP120

1. LP# pulled low

Shutdown

2. AUX, Main link inputs and outputs are disabled

3. Most IC circuitry is shut down for ultra low power

consumption

4. HPD_SRC reflects HPD_SINK

Any State

→ Output

Invalid DPCD write value to register 101h or 103h

1. OUTx becomes disabled

Disable Mode

6

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