AN2131SC Cypress Semiconductor Corp, AN2131SC Datasheet - Page 192

• Manufacturer Part Number: AN2131SC
• Description: IC MCU 8051 8K RAM 24MHZ 44QFP
• Manufacturer: Cypress Semiconductor Corp
• Series: EZ-USB®r

Specifications of AN2131SC

• Applications: USB Microcontroller
• Core Processor: 8051
• Program Memory Type: ROMless
• Controller Series: AN213x
• Ram Size: 8K x 8
• Interface: I²C, USB
• Number Of I /o: 16
• Voltage - Supply: 3 V ~ 3.6 V
• Operating Temperature: 0°C ~ 70°C
• Mounting Type: Surface Mount
• Package / Case: 44-QFP
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Other names: 428-1306; AN2131SC

When a USB device is suspended, the hub driver is tri-stated, and the bus pullup and pull-
down resistors cause the bus to assume the “J,” or idle state. A suspended device signals a
remote wakeup by asserting the “K” state for 10-15 ms. The 8051 controls this using the
SIGRSUME bit in the USBCS register.
If the 8051 finds WAKESRC=1 after exiting the idle mode, it drives the “K” state for 10-
15 ms to signal the USB remote wakeup. It does this by setting SIGRSUME=1, waiting
10-15 ms, and then setting SIGRSUME=0. When SIGRSUME=0, the EZ-USB bus buffer
reverts to normal operation. The resume routine should also write a “1” to the WAKESRC
bit to clear it.
The USB Default device does not support remote wakeup. This fact is reported at enu-
meration time in byte 7 of the built-in Configuration Descriptor (Table 5-10).
EZ-USB TRM v1.9
Note
If your design does not use remote wakeup, tie the WAKEUP# pin high. Holding the
WAKEUP# pin low inhibits the EZ-USB chip from suspending.
J and K States
The USB Specification uses differential data signals D+ and D-. Instead of defining a
logical “1” and “0,” it defines the “J” and “K” states. For a high speed device, the “J”
state means (D+ > D-).
Remote Wakeup: The Big Picture
Additional factors besides the EZ-USB suspend-resume mechanism described in this
section determine whether remote wakeup is possible. These are:
1.
2.
The device must report that it is capable of signaling a remote wakeup in the “bAt-
tributes” field of its Configuration Descriptor. See Table 5-10 for an example of this
descriptor.
The host must issue a “Set_Feature/Device” request with the feature selector field
set to 0x01 to enable remote wakeup. See Table 7-6 for the detailed request.
Chapter 11. EZ-USB Power Management
Page 11-5