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Semiconductor Group
23
Memory Organization
4.3
General Purpose Register
The lower 32 locations of the internal RAM are assigned to four banks with eight general purpose
register (GPRs) each. Only one of these banks may be enabled at a time. Two bits in the program
status word, PSW.3 and PSW.4, select the active register bank (see description of the PSW). This
allows fast context switching, which is useful when entering subroutines or interrupt service
routines. ASM51 and the device SAB 80(C)515 default to register bank 0.
The 8 general purpose registers of the selected register bank may be accessed by register
addressing. With register addressing the instruction op code indicates which register is to be used.
For indirect accessing R0 and R1 are used as pointer or index register to address internal or
external memory (e.g. MOV @R0).
Reset initializes the stack pointer to location 07H and increments it once to start from location 08H
which is also the first register (R0) of register bank 1. Thus, if one is going to use more than one
register bank, the SP should be initiated to a different location of the RAM which is not used for data
storage.
4.4
Special Function Registers
The Special Function Register (SFR) area has two important functions. Firstly, all CPU register
except the program counter and the four register banks reside here. The CPU registers are the
arithmetic registers like A, B, PSW and pointers like SP, DPH and DPL.
Secondly, a number of registers constitute the interface between the CPU and all on-chip
peripherals. That means, all control and data transfers from and to the peripherals use this register
interface exclusively.
The special function register area is located in the address space above the internal RAM from
addresses 80H to FFH. All 41 special function registers of the SAB 80(C)515 reside here.
Fifteen SFRs, that are located on addresses dividable by eight, are bit-addressable, thus allowing
128 bit-addressable locations within the SFR area.
Since the SFR area is memory mapped, access to the special function registers is as easy as with
internal RAM, and they may be processed with most instructions. In addition, if the special functions
are not used, some of them may be used as general scratch pad registers. Note, however, all SFRs
can be accessed by direct addressing only.
The special function registers are listed in table 4-1. Bit- and byte-addressable special function
registers are marked with an asterisk at the symbol name.
*
Содержание SAB 80515 Series
Страница 9: ...Semiconductor Group 9 Introduction Figure 1 2 Block Diagram ...
Страница 12: ...Semiconductor Group 12 Fundamental Structure Figure 2 1 Detailed Block Diagram ...
Страница 18: ...Semiconductor Group 18 Central Processing Unit Figure 3 1 Fetch Execute Sequence ...
Страница 22: ...Semiconductor Group 22 Memory Organization Figure 4 3 Mapping of the Lower Portion of the Internal Data Memory ...
Страница 30: ...Semiconductor Group 30 External Bus Interface Figure 5 1 a and b External Program Memory Execution ...
Страница 38: ...Semiconductor Group 38 On Chip Peripheral Components Figure 7 3 Output Driver Circuits of Ports 1 through 5 ...
Страница 59: ...Semiconductor Group 59 On Chip Peripheral Components Figure 7 16 a Functional Diagram Serial Interface Mode 0 ...
Страница 60: ...Semiconductor Group 60 On Chip Peripheral Components Figure 7 16 b Timing Diagram Serial Interface Mode 0 ...
Страница 61: ...Semiconductor Group 61 On Chip Peripheral Components Figure 7 17 a Functional Diagram Serial Interface Mode 1 ...
Страница 62: ...Semiconductor Group 62 On Chip Peripheral Components Figure 7 17 b Timing Diagram Serial Interface Mode 1 ...
Страница 73: ...Semiconductor Group 73 On Chip Peripheral Components Figure 7 25 A D Converter Block Diagram ...
Страница 83: ...Semiconductor Group 83 On Chip Peripheral Components Figure 7 33 a Timer 2 Block Diagram ...
Страница 111: ...Semiconductor Group 111 On Chip Peripheral Components Figure 7 54 Timing Diagram System Clock Output ...
Страница 113: ...Semiconductor Group 113 Interrupt System Figure 8 1 a Interrupt Structure of the SAB 80 C 515 80 C 535 ...
Страница 114: ...Semiconductor Group 114 Interrupt System Figure 8 1 b Interrupt Structure of the SAB 80 C 515 80 C 535 cont d ...
Страница 204: ...Semiconductor Group 204 Instruction Set XCH A Ri Operation XCH A Ri Bytes 1 Cycles 1 Encoding 1 1 0 0 0 1 1 i ...
Страница 215: ...Device Specifications Semiconductor Group 215 ...
Страница 217: ...Device Specifications Semiconductor Group 217 Pin Configuration P LCC 68 ...
Страница 219: ...Device Specifications Semiconductor Group 219 Logic Symbol ...
Страница 226: ...Device Specifications Semiconductor Group 226 Figure 1 Block Diagram ...
Страница 229: ...Device Specifications Semiconductor Group 229 Figure 2 Memory Address Spaces ...
Страница 239: ...Device Specifications Semiconductor Group 239 Figure 4 Block Diagram of the A D Converter ...
Страница 241: ...Device Specifications Semiconductor Group 241 Figure 5 Interrupt Request Sources ...
Страница 242: ...Device Specifications Semiconductor Group 242 Figure 6 Interrupt Priority Level Structure ...
Страница 268: ...Device Specifications Semiconductor Group 268 AC Testing Input Output Waveforms AC Testing Float Waveforms ...