at43usb320a ATMEL Corporation, at43usb320a Datasheet - Page 22

• Manufacturer Part Number: at43usb320a
• Description: Full-speed Usb Microcontroller With An Embedded Hub
• Manufacturer: ATMEL Corporation

Figure 5. AT43USB320A Interrupt Structure
Reset Sources
22
AT43USB320A
RESERVED
GLB SUSP
FRMWUP
The AT43USB320A has four sources of reset:
•
•
•
•
When the USB hardware is reset, the compound device is de-configured and has to be re-
enumerated by the host. When the microcontroller is reset, all I/O registers are then set to their
initial values, and the program starts execution from address $000. The instruction placed in
address $000 must be a JMP instruction to the reset handling routine. If the program never
enables an interrupt source, the interrupt vectors are not used, and regular program code can
be placed at these locations. The circuit diagram in Figure 6 shows the reset logic. The user
can select the start-up time according to typical oscillator start-up. The number of WDT oscilla-
tor cycles used for each time-out is shown in Table 7.
EOF1
EOF2
HEP0
FEP2
FEP1
FEP0
RSM
SOF
Power-on Reset – The MCU is reset when the supply voltage is below the power-on reset
threshold.
External Reset – The MCU is reset when a low level is present on the RESET pin for
more than 50 ns.
Watchdog Reset – The MCU is reset when the watchdog timer period expires and the
watchdog is enabled.
USB Reset – A USB bus reset is defined as a SE0 (single ended zero) of at least 4 slow
speed USB clock cycles received by Port0. The internal reset pulse to the USB hardware
and microcontroller lasts for 24 oscillator periods.
Suspend/Resume
Status Register
USB Interrupt
Register
Suspend/Resume
Enable Register
Interrupt Enable
USB Interrupt
Register
INT0, SUSP/RSM
TIMER1 COMPB
TIMER1 COMPA
TIMER1 CAPT
TIMER0 OVF
TIMER1 OVF
UART UDRE
USB
UART RX
UART TX
SPI STC
RESET
INT1
Microcontroller
12
13
11
10
9
8
7
6
5
4
3
2
1
Interrupt
Logic
1443E–USB–4/04