DS87C550 High-Speed Microcontroller User’s Guide Supplement
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Data Pointer Low 1 (DPL1)
76543210
SFR 84h DPL1.7 DPL1.6 DPL1.5 DPL1.4 DPL1.3 DPL1.2 DPL1.1 DL1H.0
RW-0 RW-0 RW-0 RW-0 RW-0 RW-0 RW-0 RW-0
R=Unrestricted Read, W=Unrestricted Write, -n=Value after Reset
DPL1.7-0
Bits 7-0 Data Pointer Low 1. This register is the low byte of the auxiliary 16-bit data
pointer. When the SEL bit (DPS.0) is set, DPL1 and DPH1 are used in place of
DPL and DPH during DPTR operations.
Data Pointer High 1 (DPH1)
76543210
SFR 85h DPH1.7 DPH1.6 DPH1.5 DPH1.4 DPH1.3 DPH1.2 DPH1.1 DPH1.0
RW-0 RW-0 RW-0 RW-0 RW-0 RW-0 RW-0 RW-0
R=Unrestricted Read, W=Unrestricted Write, -n=Value after Reset
DPH1.7-0
Bits 7-0 Data Pointer High 1. This register is the high byte of the auxiliary 16-bit data
pointer. When the SEL bit (DPS.0) is set, DPL1 and DPH1 are used in place of
DPL and DPH during DPTR operations.
Data Pointer Select (DPS)
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SFR86hID1ID0TSL0----SEL
RW-0 RW-0 RW-0 R-0 R-0 R-0 R-0 RW-0
R=Unrestricted Read, W=Unrestricted Write, -n=Value after Reset
ID1, ID0
Bits 7-6 Increment/Decrement Select Bits These bits define how the INC DPTR
instruction functions in relation to the current DPTR as selected by SEL.
ID1 ID0 SEL = 0 SEL = 1
0 0 Increment DPTR Increment DPTR1
0 1 Decrement DPTR Increment DPTR1
1 0 Increment DPTR Decrement DPTR1
1 1 Decrement DPTR Decrement DPTR1
TSL
Bit 5 Toggle Select Bit Enable This bit allows any instruction involving the data
pointer to toggle the SEL bit automatically. When this bit is logic 1, the SEL
bit will automatically toggle, otherwise it will not.
Bits 4-1 Reserved. Read will be indeterminate.
SEL
Bit 0 Data Pointer Select. This bit selects the active data pointer.
0 = Instructions that use the DPTR will use DPL and DPH.
1= Instructions that use the DPTR will use DPL1 and DPH1.
