AFAIK, all DPTR instructions for the Dallas DS89C4x0's select the "active" DPTR.

There are several modes in which the DPTR can be addressed. There are also several modes in which it can be used. For example, you can have the DPTR auto-increment (or auto-decrement) each time it is addressed, and you can have the MCU toggle which DPTR is the active one on each DPTR access, thereby allowing you to move data from one location to another without having to modify the DPTRs between uses. You can auto increment one DPTR while leaving the other unchanged, even when toggling between DPTR's. If none of those special modes are enabled, the Dallas MCU will use the default (DPTR0) at the classic DPTR SFR location in the classic way. Aside from the toggle mode, which inherently affects both DPTRs, all these features are individually programmable for each DPTR.

RE