EM78M680 Datasheet, PDF (29/53 Pages) ELAN Microelectronics Corp – USB Full Speed Microcontroller

Contents
Only when the global interrupt is enabled by the ENI instruction that the individual
interrupt will work. After DISI instruction, any interrupt will not work even if the
respective control bits of IOCF are set to 1.
The USB Host Resume Interrupt works only under Dual clock mode. This is
because when the MCU is under sleep mode, it will be waked up by the UDC
Resume signal automatically
6.4 USB Device Controller
The USB Device Controller (UDC) built-in in the EM78M680 can interpret the USB
Standard Command and response automatically without involving firmware. The
embedded Series Interface Engine (SIE) handles the serialization and
de-serialization of actual USB transmission. Thus, a developer can concentrate
his efforts more in perfecting the device actual functions and spend less energy in
dealing with USB transaction.
The UDC handles and decodes most Standard USB commands defined in the
USB Specification Rev 1.1. If the UDC receives an unsupported command, it will
set a flag to notify the MCU the receipt of such command.
Each time the UDC receives a USB command, it writes the command into EP0’s
FIFO. Only when it receives unsupported command that the UDC will notify the
MCU through interrupt.
Therefore, the EM78M680 is very flexible for USB applications since developers
can freely choose the method of decoding the USB command as dictated by
different situation.
6.5 Device Address and Endpoints
The EM78M680 supports one device address and five endpoints, EP0 for control
endpoint, EP1 ~ EP5 for interrupt/bulk /isochronous endpoints. Sending data to
USB host in EM78M680 is very easy. Just write data into the EP’s FIFO, then set
the flag, and the UDC will handle the rest. It will then confirm that the USB host has
received the correct data from the EM78M680.
6.6 Reset
The EM78M680 provides three types of reset: (1) Power-on Reset, (2) Watchdog
Reset, and (3) USB Reset.
6.6.1 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 the following predetermined states (see below), and then, it
is ready to execute the program.
a. The program counter is cleared.
b. The TCC timer and Watchdog timer are cleared.
Product Specification (V1.11) 02.10.2007
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