Cypress CY7C68300C/CY7C68301C CY7C68320C/CY7C68321C, Vbusataenable, Atapuen, PWR500#, Vbuspwrd

CY7C68300C/CY7C68301C

CY7C68320C/CY7C68321C

interface and the attached mass storage device, especially if Ultra DMA Mode is used.

VBUS_ATA_ENABLE

VBUS_ATA_ENABLE is typically used to indicate to the AT2LP that power is present on VBUS. This pin is polled by the AT2LP at startup and then every 20 ms thereafter. If this pin is ‘0’, the AT2LP releases the pull up on D+ as required by the USB specification.

Also, if bit 4 of configuration address 0x08 is ‘1’, the ATA interface pins are placed in a Hi-Z state when VBUS_ATA_ENABLE is ‘0’. If bit 4 of configuration address 0x08 is ‘0’, the ATA interface pins are still driven when VBUS_ATA_ENABLE is ‘0’.

ATAPUEN

This output can be used to control the required host pull up resistors on the ATA interface in a bus-powered design to minimize unnecessary power consumption when the AT2LP is in suspend. ATAPUEN is driven to ‘0’ when the ATA bus is inactive. ATAPUEN is driven to ‘1’ when the ATA bus is active. ATAPUEN is set to a Hi-Z state along with all other ATA interface pins if VBUS_ATA_ENABLE is deasserted and the ATA_EN functionality (bit 4 of configuration address 0x08) is enabled (0).

ATAPUEN can also be configured as a GPIO input. See “HID Functions for Button Controls” on page 15 for more infor- mation on HID functionality.

PWR500#

The AT2LP asserts PWR500# to indicate that VBUS current may be drawn up to the limit specified by the bMaxPower field of the USB configuration descriptors. If the AT2LP enters a low-power state, PWR500# is deasserted. When normal operation is resumed, PWR500# is restored. The PWR500# pin must never be used to control power sources for the AT2LP. In the 56-pin package, PWR500# only functions during bus-powered operation.

PWR500# can also be configured as a GPIO input. See “HID Functions for Button Controls” on page 15 for more infor- mation on HID functionality.

VBUSPWRD

VBUSPWRD is used to indicate self- or bus-powered operation. Some designs require the ability to operate in either self- or bus-powered modes. The VBUSPWRD input pin enables these devices to switch between self-powered and bus-powered modes by changing the contents of the bMaxPower field and the self-powered bit in the reported configuration descriptors (see Table 4).

Note that current USB host drivers do not poll the device for this information, so the effect of this pin is only seen on a USB or power on reset.

Table 4. Behavior of Descriptor Data that is Dependent Upon VBUSPWRD State

Pin	VBUSPWRD = ‘1’	VBUSPWRD = ‘0’	VBUSPWRD N/A (56-pin)
bMaxPower	0xFA	0x01	The value from configuration
Reported Value	(500 mA)	(2 mA)	address 0x34 is used.
bmAttributes bit 6	‘0’	‘1’	‘0’ if bMaxPower > 0x01
Reported Value	(bus-powered)	(self-powered)	‘1’ if bMaxPower ≤ 0x01

RESET#

Asserting RESET# for 10 ms resets the entire AT2LP. In self-powered designs, this pin is normally tied to VCC through a 100k resistor, and to GND through a 0.1 μF capacitor, as shown in Figure 9.

Cypress does not recommend an RC reset circuit for bus-powered devices because of the potential for VBUS voltage drop, which may result in a startup time that exceeds the USB limit. Refer to the application note titled EZ-USB FX2™/AT2™/SX2™ Reset and Power Considerations, at www.cypress.com, for more information.

While the AT2LP is in reset, all pins are held at their default startup state.

Figure 9. R/C Reset Circuit for Self-powered Designs

100KΩ

RESET#

0.1μF

Document 001-05809 Rev. *A Page 14 of 42

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