ST ST10 Series - Page 7

PROGRAMMING MANUAL Standard Instruction Set
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Long addresses (16-bit) are treated in two parts. Bits 13...0 specify a 14-bit data page offset,
and bits 15...14 specify the Data Page Pointer (1 of 4). The DPP is used to generate the
physical 24-bit address (see figure below).
All ST10 devices support an address space of up to 16 MByte, so only the lower ten bits of
the selected DPP register content are concatenated with the 14-bit data page offset to build
the physical address.
The long addressing mode is referred to by the mnemonic “mem”.
Figure 1 Interpretation of a 16-bit long address
Mnemo Physical Address Long Address Range Scope of Access
mem (DPP0) || mem^3FFFh 0000h...3FFFh Any Word or Byte
(DPP1) || mem^3FFFh 4000h...7FFFh
(DPP2) || mem^3FFFh 8000h...BFFFh
(DPP3) || mem^3FFFh C000h...FFFFh
mem pag || mem^3FFFh 0000h...FFFFh (14-bit) Any Word or Byte
mem seg || mem 0000h...FFFFh (16-bit) Any Word or Byte
Table 2 Summary of long address modes
0
15
14 13
16-bit Long Address
DPP0
DPP1
DPP2
DPP3
14-bit page offset
24-bit Physical Address
selects Data Page Pointer
0
9
023
1314