Intel MCS 51 - Special Function Registers

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8XC51FX HARDWARE DESCRIPTION
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rlgure i. =Ak.alrA rurwuonal DIUGKwagram
accessesthe SFR at location OAOH(which is P2). In-
3.0 SPECIAL FUNCTION REGISTERS
structionsthatuseindirectaddressingaccess
the upper
128bytes of data IUM. For example:
A map of the on-chip memory area called the SFR
(Speciaf Function Register)space is shown in Table 2.
MOV @RO,#data
Note that not alf of the addresses are occupied. Unoc-
whereROcontains OAOH,accessesthe data byte at ad-
cupied addresses are not implemented on the chip.
dress OAOH,rather than P2 (whose address is OAOH).
Read aweases to these addresseswill in generafreturn
Note that stack operationsare examplesof indireet ad-
random dam and write aeceaseswill have no effect.
dressing,so the upper 128bytes of dataIWM areavail-
able as stack space.
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