EZ-USB Datasheet, PDF (189/334 Pages) Cypress Semiconductor – The EZ-USB USB Integrated Circuit

11.2 Suspend
12 MHz
STOP
Oscillator
PLL
No USB activity
for 3 msec.
48 MHz
div by
2
PCON.0
8051
USB
"SUSPEND"
Interrupt
INT2
CLK24
Figure 11-2. EZ-USB Suspend Sequence
A USB device recognizes SUSPEND as 3 ms of a bus idle (“J”) state. The EZ-USB core
alerts the 8051 by asserting the USB (INT2) interrupt and the SUSPEND interrupt vector.
This gives the 8051 code a chance to perform power SUSPEND interrupt vector. This
gives the 8051 code a chance to perform power conservation housekeeping before shut-
ting down the oscillator.
Page 11-2
Chapter 11. EZ-USB Power Management
EZ-USB TRM v1.9