EM78612 Datasheet, PDF (23/28 Pages) ELAN Microelectronics Corp – Universal Serial Bus Microcontroller

EM78612
Universal Serial Bus Microcontroller
7.4.3 Device Address and Endpoints
EM78612 supports one device address, two endpoints, EP0 for control endpoint, and
EP1 for interrupt endpoint. Sending data to USB host in EM78612 is very easy. Just
write data into EP’s FIFO, then set flag, and the UDC will handle the rest. It will then
confirm that the USB host has received the correct data from EM78612.
7.5 Reset
The EM78612 provides three types of reset: (1) Power-on Reset, (2) WatchDog
Reset, and (3) USB Reset.
7.5.1 Power-On Reset
Power-on Reset occurs when the device is attached to power and a reset signal is
initiated. The signal will last until the MCU becomes stable. After a Power-on Reset,
the MCU enters into following predetermined states (see below), and then, it is ready
to execute the program.
1. The program counter is cleared.
2. The TCC timer and WatchDog timer are cleared.
3. Special registers and Special Control registers are all set to initial value.
The MCU also has a low voltage detector that detects low output power condition.
Whenever the output voltage of the 3.3V regulator decreases to below 2.2V, a reset
signal is set off.
7.5.2 WatchDog Reset
When the WatchDog timer overflows, it causes the WatchDog to reset. After it
resets, the program is executed from the beginning and some registers will be reset.
The UDC however, remains unaffected.
7.5.3 USB Reset
When UDC detects a USB Reset signal on USB Bus, it interrupts the MCU, then
proceed to perform the specified process that follows.
7.6 Power Saving Mode
The EM78612 provides two options of power saving modes for energy conservation,
i.e., Power Down mode, and Dual Clock mode.
7.6.1 Power Down Mode
The EM78612 enters into Power Down mode by clearing the RUN register (IOCE[4]).
During this mode, the oscillator is turned off and the MCU goes to sleep. It will wake
up when signal from USB host is resumed, or when the WatchDog resets, or the input
port state changes.
Product Specification (V1.1) 04.28.2004
19
(This specification is subject to change without further notice)