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Module 2: The 8051 Architecture

20227m

Explain the PSW flags and SFR's (Special function registers) of 8051 microcontroller and also write the type of SFR's.

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PSW Flags & SFR Types

PSW flags (D0H, bit-addressable): CY (7) carry, AC (6) aux carry, F0(5) user, RS1(4) RS0(3) bank select, OV(2) overflow, - (1) reserved, P(0) parity. Flags updated by arithmetic/logic: ADD affects CY,AC,OV,P etc.

SFR Types:

  • Port SFRs: P0,P1,P2,P3
  • Timer SFRs: TMOD,TCON,TH0,TL0,TH1,TL1
  • Serial SFRs: SCON,SBUF,PCON
  • Interrupt SFRs: IE,IP
  • Control SFRs: PSW,SP,ACC,B,DPL,DPH
  • Power/Misc: PCON

21 core SFRs in 80-FFH, accessed by direct addressing only, 11 bit-addressable. Control whole MCU.

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