參數(shù)資料
型號： SAB83C517A-5N18-T4
文件頁數(shù)： 21/77頁
文件大小： 1358K
代理商： SAB83C517A-5N18-T4
SAB 80C517A/83C517A-5
Semiconductor Group
20
1994-05-01
Accesses to XRAM
Because the XRAM is used in the same way as external data memory the same instruction
types must be used for accessing the XRAM.
Note:
If a reset occurs during a write operation to XRAM, the effect on XRAM depends on the
cycle which the reset is detected at (MOVX is a 2-cycle instruction):
Reset detection at cycle 1:
The new value will not be written to XRAM. The old value
is not affected.
Reset detection at cycle 2:
The old value in XRAM is overwritten by the new value.
Accesses to XRAM using the DPTR
There are a Read and a Write instruction from and to XRAM which use one of the 16-bit DPTR
for indirect addressing. The instructions are:
MOVX A,
@DPTR (Read)
MOVX
@DPTR, A (Write)
Normally the use of these instructions would use a physically external memory. However, in the
SAB 80C517A the XRAM is accessed if it is enabled and if the DPTR points to the XRAM
address space (DPTR F800
H
).
Accesses to XRAM using the Registers R0/R1
The 8051 architecture provides also instructions for accesses to external data memory range
which use only an 8-bit address (indirect addressing with registers R0 or R1). The instructions
are:
MOVX A,
@Ri (Read)
MOVX
@Ri, A (Write)
In application systems, either a real 8-bit bus (with 8-bit address) is used or Port 2 serves as
page register which selects pages of 256-byte. However, the distinction, whether Port 2 is
used as general purpose I/O or as "page address" is made by the external system design. From
the device’s point of view it cannot be decided whether the Port 2 data is used externally as
address or as I/O data!
Hence, a special page register is implemented into the SAB 80C517A to provide the possibility
of accessing the XRAM also with the MOVX @Ri instructions, i.e. XPAGE serves the same
function for the XRAM as Port 2 for external data memory.
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相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
SAB83C517A-N18-T4 制造商:INFINEON 制造商全稱:Infineon Technologies AG 功能描述:8-Bit CMOS Single-Chip Microcontroller
SAB88C166 制造商:INFINEON 制造商全稱:Infineon Technologies AG 功能描述:16-Bit CMOS Single-Chip Microcontrollers with/without oscillator prescaler with 32 KByte Flash EPROM
SAB88C166-5M 制造商:INFINEON 制造商全稱:Infineon Technologies AG 功能描述:16-Bit CMOS Single-Chip Microcontrollers with/without oscillator prescaler with 32 KByte Flash EPROM
SAB88C166EVAL 制造商:Siemens 功能描述:
SAB88C166W-5M 制造商:INFINEON 制造商全稱:Infineon Technologies AG 功能描述:16-Bit CMOS Single-Chip Microcontrollers with/without oscillator prescaler with 32 KByte Flash EPROM
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