Philips CEM2100/00, Руководство по обслуживанию

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3. Interrupt Control Circuit
3.4 Software Interrupt (INTSW)
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5CL8
Interrupt requests are sampled during the final cycle of the instruction being executed. Thus, the next inter-
rupt can be accepted immediately after the interrupt return instruction is executed.
Note 1: It is recommended that stack pointer be return to rate before INTATRAP (Increment 3 times), if return inter-
rupt instruction [RETN] is not utilized during interrupt service program under INTATRAP (such as Example
2).
Note 2: When the interrupt processing time is longer than the interrupt request generation time, the interrupt service
task is performed but not the main task.
3.4 Software Interrupt (INTSW)
Executing the SWI instruction generates a software interrupt and immediately starts interrupt processing (INTSW
is highest prioritized interrupt).
Use the SWI instruction only for detection of the address error or for debugging.
3.4.1 Address error detection
FFH is read if for some cause such as noise the CPU attempts to fetch an instruction from a non-existent
memory address during single chip mode. Code FFH is the SWI instruction, so a software interrupt is gener-
ated and an address error is detected. The address error detection range can be further expanded by writing
FFH to unused areas of the program memory. Address trap reset is generated in case that an instruction is
fetched from RAM, DBR or SFR areas.
3.4.2 Debugging
Debugging efficiency can be increased by placing the SWI instruction at the software break point setting
address.
3.5 Undefined Instruction Interrupt (INTUNDEF)
Taking code which is not defined as authorized instruction for instruction causes INTUNDEF. INTUNDEF is gen-
erated when the CPU fetches such a code and tries to execute it. INTUNDEF is accepted even if non-maskable inter-
rupt is in process. Contemporary process is broken and INTUNDEF interrupt process starts, soon after it is
requested.
Note: The undefined instruction interrupt (INTUNDEF) forces CPU to jump into vector address, as software interrupt
(SWI) does.
3.6 Address Trap Interrupt (INTATRAP)
Fetching instruction from unauthorized area for instructions (Address trapped area) causes reset output or address
trap interrupt (INTATRAP). INTATRAP is accepted even if non-maskable interrupt is in process. Contemporary pro-
cess is broken and INTATRAP interrupt process starts, soon after it is requested.
Note: The operating mode under address trapped, whether to be reset output or interrupt processing, is selected on
watchdog timer control register (WDTCR).
Example 2 :Restarting without returning interrupt
(In this case, PSW (Includes IMF) before interrupt acceptance is discarded.)
PINTxx: INC SP ; Recover SP by 3
INC SP ;
INC SP ;
(interrupt processing)
LD EIRL, data ; Set IMF to “1” or clear it to “0”
JP Restart Address ; Jump into restarting address