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ST90E158LV Ver la hoja de datos (PDF) - STMicroelectronics

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ST90E158LV 8/16-BIT MCU FAMILY WITH UP TO 64K ROM/OTP/EPROM AND UP TO 2K RAM ST-Microelectronics
STMicroelectronics ST-Microelectronics
ST90E158LV Datasheet PDF : 190 Pages
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ST90158 - DEVICE ARCHITECTURE
ADDRESS SPACE EXTENSION (Cont’d)
2.6.2 Addressing 64-Kbyte Segments
This extension mode is used to address Data
memory space during a DMA and Program mem-
ory space during any code execution (normal code
and interrupt routines).
Three registers are used: CSR, ISR, and DMASR.
The 6-bit contents of one of the registers CSR,
ISR, or DMASR define one out of 64 Memory seg-
ments of 64 Kbytes within the 4 Mbytes address
space. The register contents represent the 6
MSBs of the memory address, whereas the 16
LSBs of the address (intra-segment address) are
given by the virtual 16-bit address (see Figure 15).
2.7 MMU REGISTERS
The MMU uses 7 registers mapped into Group F,
Page 21 of the Register File and 2 bits of the
EMR2 register.
Most of these registers do not have a default value
after reset.
2.7.1 DPR[3:0]: Data Page Registers
The DPR[3:0] registers allow access to the entire 4
Mbyte memory space composed of 256 pages of
16 Kbytes.
2.7.1.1 Data Page Register Relocation
If these registers are to be used frequently, they
may be relocated in register group E, by program-
ming bit 5 of the EMR2-R246 register in page 21. If
this bit is set, the DPR[3:0] registers are located at
R224-227 in place of the Port 0-3 Data Registers,
which are re-mapped to the default DPR’s loca-
tions: R240-243 page 21.
Data Page Register relocation is illustrated in Fig-
ure 13.
Figure 15. Addressing via CSR, ISR, and DMASR
CSR
MMU registers
DMASR
ISR
16-bit virtual address
1
1 Fetching program
instruction
2 Data Memory
accessed in DMA
Fetching interrupt
3 instruction or DMA
access to Program
Memory
2
3
6 bits
22-bit physical address
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