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AT89LP51 数据表(PDF) 28 Page - ATMEL Corporation |
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AT89LP51 数据表(HTML) 28 Page - ATMEL Corporation |
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28 / 113 page  28 3709C–MICRO–5/11 AT89LP51/52 - Preliminary The data pointer update bits, DPU1 and DPU0, allow MOVX @DPTR and MOVC @DPTR instructions to update the selected data pointer automatically in a post-increment or post-decre- ment fashion. The direction of update depends on the DPD1 and DPD0 bits as shown in Table 5-4. These bits can be used to make block copy routines more efficient. Table 5-2. Data Pointer Decrement Behavior DPD1 DPD0 Equivalent Operation for INC DPTR and INC /DPTR DPS = 0 DPS = 1 INC DPTR INC /DPTR INC DPTR INC /DPTR 0 0 INC DPTR0 INC DPTR1 INC DPTR1 INC DPTR0 0 1 DEC DPTR0 INC DPTR1 INC DPTR1 DEC DPTR0 1 0 INC DPTR0 DEC DPTR1 DEC DPTR1 INC DPTR0 1 1 DEC DPTR0 DEC DPTR1 DEC DPTR1 DEC DPTR0 Table 5-3. AUXR1 – Data Pointer Configuration Register AUXR1 = A2H Reset Value = 0000 00X0B Not Bit Addressable DPU1 DPU0 DPD1 DPD0 SIGEN 0 – DPS Bit 7 6 543 21 0 Symbol Function DPU1 Data Pointer 1 Update. When set, MOVX @DPTR and MOVC @DPTR instructions that use DPTR1 will also update DPTR1 based on DPD1. If DPD1 = 0 the operation is post-increment and if DPD1 = 1 the operation is post-decrement. When DPU1 = 0, DPTR1 is not updated. DPU0 Data Pointer 0 Update. When set, MOVX @DPTR and MOVC @DPTR instructions that use DPTR0 will also update DPTR0 based on DPD0. If DPD0 = 0 the operation is post-increment and if DPD0 = 1 the operation is post-decrement. When DPU0 = 0, DPTR0 is not updated. DPD1 Data Pointer 1 Decrement. When set, INC DPTR instructions targeted to DPTR1 will decrement DPTR1. When cleared, INC DPTR instructions will increment DPTR1. DPD1 also determines the direction of auto-update for DPTR1 when DPU1 = 1. DPD0 Data Pointer 0 Decrement. When set, INC DPTR instructions targeted to DPTR0 will decrement DPTR0. When cleared, INC DPTR instructions will increment DPTR0. DPD0 also determines the direction of auto-update for DPTR0 when DPU0 = 1. SIGEN Signature Enable. When SIGEN = 1 all MOVC @DPTR instructions and all IAP accesses will target the signature array memory. When SIGEN = 0, all MOVC and IAP accesses target CODE memory. DPS Data Pointer Select. DPS selects the active data pointer for instructions that reference DPTR. When DPS = 0, DPTR will target DPTR0 and /DPTR will target DPTR1. When DPS = 1, DPTR will target DPTR1 and /DPTR will target DPTR0. Table 5-4. Data Pointer Auto-Update DPD1 DPD0 Update Operation for MOVX and MOVC (DPU1 = 1 & DPU0 = 1) DPS = 0 DPS = 1 DPTR /DPTR DPTR /DPTR 0 0 DPTR0++ DPTR1++ DPTR1++ DPTR0++ 0 1 DPTR0-- DPTR1++ DPTR1++ DPTR0-- 1 0 DPTR0++ DPTR1-- DPTR1-- DPTR0++ 1 1 DPTR0-- DPTR1-- DPTR1-- DPTR0-- |
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