Interrupt Registers
IRQ enable flag
Address
00C1H
Name
Bit 7
-
Bit 6
-
Bit 5
INT1
Bit 4
INT0
Bit 3
P3
Bit 2
TM0
Bit 1
USB
R
W
Bit 0
-
IRQ_EN
√
√
Program can enable (setting to “1”) or disable (clearing to “0”) the ability of triggering IRQ through this
register.
z
z
z
z
USB: USB finishes Rx or Tx data
TM0: Timer0 underflow
P3: Falling edge trigger signal occurs at port 3 input mode
INT0, INT1: Falling edge trigger signal occurs at P0.4 and P0.5 input mode
IRQ status flag
Address
Name
Bit 7
-
Bit 6
-
Bit 5
INT1
Bit 4
INT0
Bit 3
P3
Bit 2
TM0
Bit 1
USB
R
W
-
Bit 0
-
00C2H
IRQ_ST
√
When IRQ occurs, program can read this register to know which source triggering IRQ.
IRQ clear flag
Address
00C3H
Name
Bit 7
-
Bit 6
-
Bit 5
INT1
Bit 4
INT0
Bit 3
P3
Bit 2
TM0
Bit 1
USB
R
-
W
Bit 0
-
IRQ_CLR
√
Program can clear the interrupt event by writing ‘1’ into the corresponding bit.
Watchdog Timer (WDT)
Address
00DEH
00DFH
Name
Bit 7
RSTS
CLR
Bit 6
Bit 5
Bit 4
Bit 3
Bit 3
-
Bit 2
Bit 2
-
Bit 1
Bit 1
-
R
W
-
Bit 0
Bit 0
-
WDT_ST
WDT_CLR
-
-
-
-
-
-
√
-
√
z
z
Bit 3 ~ Bit 0: Contents of WDT
RSTS: WDT reset status, set by the hardware when WDT overflows, and clear by the firmware or
the hardware reset
z
CLR: RSTS clear and WDT reset control bit, the program can clear the RSTS bit and reset WDT
by writing “1” into the CLR bit
The watchdog timer (WDT) is organized as a 4-bit counter, which is designed to prevent the program
from unknown errors. If the WDT overflows, the WDT reset function will be performed. RSTS (Bit 7 of
WDT_ST) is set by hardware when the WDT overflows. It also can be cleared by hardware reset or
writing 1 to bit 7 of WDT_CLR. The interval of WDT to cause reset is around 0.7s at 6MHz external
oscillator. Programming one into the bit 7 of WDT_CLR register can reset the contents of the WDT. In
normal operation, the application program must reset WDT before it overflows. A WDT overflow
indicates that operation is not under control and the chip will be reset. The organization of the watchdog
timer is shown as below
MEGAWIN
MPC2F35_USB Data Sheet
9
MEGAWIN [ MEGAWIN TECHNOLOGY CO., LTD ]
