Applications Engineering
SKP16C62P User’s Manual Rev. 1.0
12 / 22
December 2003
Table 6-3. Limitations on Register Operation
Register Name
Restriction
User Interrupt Stack Pointer
Range 7B80H – 7BFFH is used by the kernel
UART1 Transmit/Receive Mode Register
UART1 Transmit/Receive Control Register 0
UART1 Transmit/Receive Control Register 1
Do not change
UART1 Interrupt Control Register 0
Do not change
UART Transmit/Receive Control Register 2
Do not change bits 0 and 2
UART1 Transmit Buffer Register
Do not write to this register
UART1 Receive Buffer Register
Do not read this register
Port 6 and Port 6 DDR
To prevent changes on P6_4 data and direction,
use read-modify-write only instructions (BSET,
BCLR, AND, OR, etc)
6.6 Limitations on Interrupts - Vectors that Reside in the Hardware Vector Table
Table 6-4 lists the limitations on hardware interrupt vector addresses.
Table 6-4. Interrupt Vector Addresses
Interrupt Cause
M16C/62P Vector
Address
Kit Specification
Undefined
FFFDCH ~ FFFDFH
User available
Overflow
FFFE0H ~ FFFE3H
User available
BRK Instruction
FFFE4H ~ FFFE7H
User inhibited
Address Match
FFFE8H ~ FFFEBH
User inhibited
Single-step
FFFECH ~ FFFEFH
User inhibited
Watchdog Timer
FFFF0H ~ FFFF3H
User available (Note 1)
DBC
FFFF4H ~ FFFF7H
User inhibited
NMI
FFFF8H ~ FFFFBH
User available
RESET
FFFFCH ~ FFFFFH
Reset vector (Note 2)
NOTES:
(1) The Watchdog Timer vector is shared with the oscillation stop and voltage detection
interrupt. The vector is available for oscillation stop and voltage detection interrupts, but
not Watchdog Timer interrupts.
(2) The kernel transparently relocates the Reset vector to FFFD8H.
6.7 Stop or Wait Mode Limitations
The kernel cannot be run in STOP or WAIT modes. Do not use the STOP or WAIT instructions in
your program.
6.8 User Program’s Real-Time Capability
Please be aware that while the kernel is in a “STOP” state, the hardware peripherals will continue
to run. Therefore, interrupts may not be serviced properly. Also, the watchdog timer will not be
serviced and will likely time out if active.
While the kernel is in a “RUN” state, there is no overhead on the application code, UNLESS a
RAM monitor window is open in KD30. This window requires periodic communication with the
MCU. This communication suspends normal application operation while servicing the request
(approximately 2000 BCLK cycles for each 16 bytes of data displayed in the window are used per
window update). The user must determine whether or not this behavior is acceptable.
electronic components distributor
