Cypress CY7C65113C manual Enabling/Disabling a USB Device, Hub Downstream Ports Status and Control

CY7C65113C

Hub Ports Speed								Address 0x4A
Bit #	7	6	5	4	3	2	1		0
Bit Name	Reserved	Reserved	Reserved	Reserved	Port 4 Speed	Port 3 Speed	Port 2 Speed		Port 1 Speed
Read/Write	R/W	R/W	R/W	R/W	R/W	R/W	R/W		R/W
Reset	0	0	0	0	0	0	0		0

Figure 16-2. Hub Ports Speed

Bit [0..3] : Port x Speed (where x = 1..4).

Set to 1 if the device plugged in to Port x is Low Speed; Set to 0 if the device plugged in to Port x is Full Speed. Bit [4..7] : Reserved.

Set to 0.

The Hub Ports Speed register is cleared to zero by reset or bus reset. This must be set by the firmware on issuing a port reset. The Reserved bits [4..7] should always read as ‘0.’

16.2Enabling/Disabling a USB Device

After a USB device connection has been detected, firmware must update status change bits in the hub status change data structure that is polled periodically by the USB host. The host responds by sending a packet that instructs the hub to reset and enable the downstream port. Firmware then sets the bit in the Hub Ports Enable register (Figure 16-3), for the downstream port. The hub repeater hardware responds to an enable bit in the Hub Ports Enable register (Figure 16-3) by enabling the downstream port, so that USB traffic can flow to and from that port.

If a port is marked enabled and is not suspended, it receives all USB traffic from the upstream port, and USB traffic from the downstream port is passed to the upstream port (unless babble is detected). Low-speed ports do not receive full-speed traffic from the upstream port.

When firmware writes to the Hub Ports Enable register (Figure 16-3) to enable a port, the port is not enabled until the end of any packet currently being transmitted. If there is no USB traffic, the port is enabled immediately.

When a USB device disconnection has been detected, firmware must update status bits in the hub change status data structure that is polled periodically by the USB host. In suspended mode, a connect or disconnect event generates an interrupt (if the hub interrupt is enabled) even if the port is disabled.

Hub Ports Enable Register								Address 0x49
Bit #	7	6	5	4	3	2	1		0
Bit Name	Reserved	Reserved	Reserved	Reserved	Port 4 Enable	Port 3 Enable	Port 2 Enable		Port 1 Enable
Read/Write	R/W	R/W	R/W	R/W	R/W	R/W	R/W		R/W
Reset	0	0	0	0	0	0	0		0
			Figure 16-3.	Hub Ports Enable Register

Bit [0..3] : Port x Enable (where x = 1..4)

Set to 1 if Port x is enabled; Set to 0 if Port x is disabled Bit [4..7] : Reserved.

Set to 0.

The Hub Ports Enable register is cleared to zero by reset or bus reset to disable all downstream ports as the default condition. A port is also disabled by internal hub hardware (enable bit cleared) if babble is detected on that downstream port. Babble is defined as:

•Any non-idle downstream traffic on an enabled downstream port at EOF2.

•Any downstream port with upstream connectivity established at EOF2 (i.e., no EOP received by EOF2).

16.3Hub Downstream Ports Status and Control

Data transfer on hub downstream ports is controlled according to the bit settings of the Hub Downstream Ports Control Register (Figure 16-4). Each downstream port is controlled by two bits, as defined in Table 16-1below. The Hub Downstream Ports Control Register is cleared upon reset or bus reset, and the reset state is the state for normal USB traffic. Any downstream port being forced must be marked as disabled (Figure 16-3) for proper operation of the hub repeater.

Firmware should use this register for driving bus reset and resume signaling to downstream ports. Controlling the port pins through this register uses standard USB edge rate control according to the speed of the port, set in the Hub Port Speed Register.

Document #: 38-08002 Rev. *D Page 30 of 49

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