可冰

系統(tǒng)手冊[2-15]
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RESET
When the nRESET signal goes LOW, ARM920T abandons the executing instruction and then continues to fetch
instructions from incrementing word addresses.
When nRESET goes HIGH again, ARM920T:
1. Overwrites R14_svc and SPSR_svc by copying the current values of the PC and CPSR into them. The value of
the saved PC and SPSR is not defined.
2. Forces M[4:0] to 10011 (Supervisor mode), sets the I and F bits in the CPSR, and clears the CPSR's T bit.
3. Forces the PC to fetch the next instruction from address 0x00.
4. Execution resumes in ARM state.
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當(dāng)~nRESET信號(低電平有效)有效時,ARM920T終止當(dāng)前指令的執(zhí)行,而連續(xù)不斷地獲取下一字地址處的指令;當(dāng)~nRESET恢復(fù)為高電平時,ARM920T執(zhí)行下面的操作:
1. 拷貝當(dāng)前PC和CPSR的值到R14_svc和SPSR_svc中.而保存過的PC和SPSR的值未定義(不確定).
2. M[4:0] <-- 10011,轉(zhuǎn)到Supervisor模式,設(shè)置CPSR中的I、F位為1(禁止中斷),并對T位清零(進(jìn)入ARM狀態(tài)).
3. 設(shè)置PC從0x00處獲取下一條指令.
4. 在ARM狀態(tài)下執(zhí)行指令.
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