Fall 2002INEL 4206 Microprocessors Lecture 4 1 Easy I Control Unit (Level 3 Flowcharts) DI → ABUS → AO fetchop1 FetchOp 00 11x opcode aoprsoprloadstorebrnjump 00 00x AO → EAB EDB → DI branch on opcode fetchop2

Fall 2002INEL 4206 Microprocessors Lecture 4 2 Easy I Control Unit State Transition Table (Part I) Curr State opcodeIAC:1 5 Next State ALU op Mem OP PC sel PC is DI le AC le AO se l AO le EDB sel reset1xx xxxxxreset2XXXNOP01X00X0X reset2xx xxxxxfetchXXXNOP X fetch00 00x1xfetchopXXXNOP11X10X0X fetch00 00x0xsoprXXXNOP11X10X0X fetch xbrn1XXXRD11X10X0X fetch xjumpXXXRD11X10X0X fetch xstore1XXXRD11X10X0X fetch xload1XXXRD11X10X0X fetch00 11x0xaoprXXXRD11X10X0X aopr00 110xxfetchANDNOP X aopr00 111xxfetchADDNOP X sopr00 000xxfetchNOTBNOP X sopr00 001xxfetchSHRBNOP X

Fall 2002INEL 4206 Microprocessors Lecture 4 3 Easy I Control Unit State Transition Table (Part II) Current State opcodeIAC: 15 Next State ALU op Mem OP PC sel PC is DI le AC le AO sel AO le EDB sel store1xx xxxxxstore2XXXNOP11X0011X store2xx xxxxxstore3XXXWR load1xx xxxxxload2XXXNOP11X0011X load2xx xxxxxload3XXXRD11X10X0X load3xx xxxxxfetchANOP X brn1xx xxxx0fetchXXXNOP X brn1xx xxxx1brn2XXXNOP X brn2xx xxxxxfetchXXXNOP X jumpxx xxxxxfetchXXXNOP X fetchop1xx xxxxxfetchXXXNOP11X0011X Can share this state

Fall 2002INEL 4206 Microprocessors Lecture 4 4 Easy-I Control Unit StateEncoding reset reset fetch 0010 aopr 0011 sopr 0100 store store store load load load brn brn jump 1101 fetchop OperationCodeOutput A000A NOTB001not B AND010A and B ADD011A + B SHRB100B / 2 4-bit Encodings for States ALU Operation Table We know how to implement this ALU ! OperationCode NOP00 ReaD01 WRite10 Control Bus Operation Table