Specification
NET2272 USB Peripheral Controller
______________________________________________________________________________
NetChip Technology, Inc., 2003
Patent Pending
335 Pioneer Way, Mountain View, California 94041
TEL (650) 526-1490
FAX (650) 526-1494
http://www.netchip.com
Rev 1.2, October 15, 2003
20
3
Reset and Initialization
3.1
Overview
The NET2272 normal initialization sequence consists of the following:
•
Assert/De-Assert RESET# pin
•
Local CPU initializes USB and local bus configuration registers
3.2
RESET# Pin
The RESET# pin causes all logic in the NET2272 to be set to its default state. It is typically connected to a power-
on reset circuit.
3.3
Root Port Reset
If the NET2272 detects a single-ended zero on the root port for greater than 2.5 microseconds, it is interpreted as a
root port reset. The root port reset is only recognized if the VBUS input pin is high, and the USB Detect Enable bit
in the USBCTL0 register is set. The following resources are reset:
•
Serial Interface Engine (SIE)
•
USB state machines
•
Local state machines
•
OURADDR Register
•
Buffer pointers
The root port reset does not affect the remainder of the configuration registers. The Root Port Reset Interrupt bit is
set when a change in the root port reset has been detected. The local CPU should take appropriate action when this
interrupt occurs.
According to the USB Specification, the width of the USB reset is minimally 10ms and may be longer depending on
the upstream host or hub. There is no specified maximum width for the USB reset.
3.4
Reset Summary
The following table shows which device resources are reset when each of the 2 reset sources are asserted.
Device
Resources
Reset Sources
USB, SIE
modules,
OURADDR,
registers
All
Configuration
Registers
Endpoint
Buffer
Pointers
RESET# pin
X
X
X
USB Root Port Reset
X
X
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