CY7C65640A

Document Number: 38-08019 Rev. *N

Page 5 of 25

Overcurrent Detection

Overcurrent detection includes timed detection of 8 ms by

default. This parameter is configured from the external EEPROM

in a range of 0 ms to 15 ms for both an enabled port and a

disabled port individually. Detection of over on downstream ports

is managed by control pins connected to an external power

switch device.

The OVR[n]# pins of the CY7C65640A series are connected to

the respective external power switch’s port overcurrent

indication (output) signals. Upon detecting an overcurrent

condition, the hub device reports the overcurrent condition to the

host and disables the PWR# output to the external power device.

Port Indicators

The USB 2.0 port indicators are also supported directly by

TetraHub. According to the specification, each downstream port

of the hub supports an optional status indicator. The presence of

indicators for downstream facing ports is specified by bit 7 of the

wHubCharacteristics field of the hub class descriptor. The

default TeraHub descriptor specifies that port indicators are

supported (wHubCharacteristics, bit 7 is set). If port indicators

are not included in the hub, EEPROM should disable this.

Each port indicator is strategically located directly on the

opposite edge of the port which it is associated with. The

indicator provides two colors: green and amber. This is

implemented as two separate LEDs, one amber and the other

green. A combination of hardware and software control is used

to inform the user of the current status of the port or the device

attached to the port and to guide the user through problem

resolution. Colors and blinking are used to provide information to

the user. The significance of the color of the LED depends on the

operational mode of the TetraHub. There are two modes of

operation for the TetraHub port indicators: automatic and

manual.

On power up, the TeraHub defaults to automatic mode, where

the color of the port indicator (green, amber, off) indicates the

functional status of the TetraHub port. In automatic mode,

TetraHub turns on the green LED whenever the port is enabled

and the amber LED when it detects an overcurrent condition. The

color of the port indicator is set by the port state machine.

Blinking of the LEDs is not supported in automatic mode. Table 1

identifies the mapping of color to port state in automatic mode.

In manual mode, the indicators are under the control of the host,

which can turn on one of the LEDs, or leave them off. This is done

by a system software USB Hub class request. Blinking of the

LEDs is supported in manual mode. The port indicators enable

the user to intervene on any error detection. For example, when

babble is detected on plugging in a defective device, or on

occurrence of an overcurrent condition, the port indicators

corresponding to the downstream port blink green or only light

the amber LED, respectively. Table 2 displays the color definition

of the indicators when TetraHub is in manual mode.

Note. Information presented in Table 1 and Table 2 is from USB 2.0 specification tables 11-6 and 11-7, respectively.

Table 1. Automatic Port State to Port Indicator Color Mapping

Port

Switching

Downstream Facing Hub Port State

Powered Off

Disconnected, Disabled, Not

Configured, Resetting, Testing

Enabled, Transmit,

or TransmitR

Suspended, Resuming,

SendEOR, Restart_E/S

With

Off or amber if due to an

overcurrent condition

Off

Green

Off

Without

Off

Off or amber if due to an

overcurrent condition

Green

Off

Table 2. Port Indicator Color Definitions in Manual Mode

Color Definition

Port State

Off

Not operational

Amber

Error condition

Green

Fully operational

Blinking Off/Green

Software attention

Blinking Off/Amber

Hardware attention

Blinking Green/Amber

Reserved

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