ECE 448 – FPGA and ASIC Design with VHDL Lecture 19 PicoBlaze Interrupt Interface & Assembly Code Development

2 ECE 448 – FPGA and ASIC Design with VHDL Required reading P. Chu, FPGA Prototyping by VHDL Examples Chapter 17, PicoBlaze Interrupt Interface Chapter 15, Assembly Code Development

Program Flow Control Instructions (1) JUMP AAA PC <= AAA JUMP C, AAA if C=1 then PC <= AAA else PC <= PC + 1 JUMP NC, AAA if C=0 then PC <= AAA else PC <= PC + 1 JUMP Z, AAA if Z=1 then PC <= AAA else PC <= PC + 1 JUMP NC, AAA if Z=0 then PC <= AAA else PC <= PC + 1

Program Flow Control Instructions (2) CALL AAA TOS <= TOS+1; STACK[TOS] <= PC; PC <= AAA CALL C | Z, AAA if C | Z =1 then TOS <= TOS+1; STACK[TOS] <= PC; PC <= AAA else PC <= PC + 1 CALL NC | NZ, AAA if C | Z =0 then TOS <= TOS+1; STACK[TOS] <= PC; PC <= AAA else PC <= PC + 1

Program Flow Control Instructions (3) RETURN (RET) PC <= STACK[TOS] + 1; TOS <= TOS - 1 RETURN C | Z (RET C | Z ) if C | Z =1 then PC <= STACK[TOS] + 1; TOS <= TOS - 1 else PC <= PC + 1 RETURN NC | NZ (RET NC | NZ ) if C | Z =0 then PC <= STACK[TOS] + 1; TOS <= TOS - 1 else PC <= PC + 1

Interrupt Related Instructions RETURNI ENABLE (RETI ENABLE) PC <= STACK[TOS] ; TOS <= TOS – 1; I <= 1; C<= PRESERVED C; Z<= PRESERVED Z RETURNI DISABLE (RETI DISABLE) PC <= STACK[TOS] ; TOS <= TOS – 1; I <= 0; C<= PRESERVED C; Z<= PRESERVED Z ENABLE INTERRUPT (EINT) I <=1; DISABLE INTERRUPT (DINT) I <=0;

7 Interrupt Flow ECE 448 – FPGA and ASIC Design with VHDL

8 Timing Diagram of an Interrupt Event ECE 448 – FPGA and ASIC Design with VHDL

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10 Interrupt Interface with a Single Event ECE 448 – FPGA and ASIC Design with VHDL

11 Interrupt Interface with Two Requests ECE 448 – FPGA and ASIC Design with VHDL

12 Interrupt Interface with a Timer ECE 448 – FPGA and ASIC Design with VHDL

13 Interrupt Interface with a Timer ECE 448 – FPGA and ASIC Design with VHDL

14 PicoBlaze Development Environments ECE 448 – FPGA and ASIC Design with VHDL

15 KCPSM3 Assembler Files ECE 448 – FPGA and ASIC Design with VHDL

16 Directives of Assembly Language ECE 448 – FPGA and ASIC Design with VHDL

17 Differences between Mnemonics of Instructions ECE 448 – FPGA and ASIC Design with VHDL

18 Differences between Mnemonics of Instructions ECE 448 – FPGA and ASIC Design with VHDL

19 Differences between Programs ECE 448 – FPGA and ASIC Design with VHDL

Example of a function in the PicoBlaze assembly language

Unsigned Multiplication – Basic Equations x =  x i  2 i i=0 k-1 p = a  x p = a  x =  a  x i  2 i = = x 0 a2 0 + x 1 a2 1 + x 2 a2 2 + … + x k-1 a2 k-1 i=0 k-1

Iterative Algorithm for Unsigned Multiplication Shift/Add Algorithm p = a  x = x 0 a2 0 + x 1 a2 1 + x 2 a2 2 + … + x k-1 a2 k-1 = (...((0 + x 0 a2 k )/2 + x 1 a2 k )/ x k-1 a2 k )/2 = k times = p (0) = 0 p = p (k) p (j+1) = (p (j) + x j a 2 k ) / 2 j=0..k-1

Unsigned Multiplication Computations pHpH pLpL 8 bits p x j a 8 bits pHpH pLpL pHpH pLpL 0 p (j+1) 2 p (j+1) p (j) + x j a 2 8 >> 1 PicoBlaze Registers p H = s5p L = s6 a = s3 x = s4 +

Unsigned Multiplication Subroutine (1) ;========================================================= ; routine: mult_soft ; function: 8-bit unsigned multiplier using ; shift-and-add algorithm ; input register: ; s3: multiplicand ; s4: multiplier ; output register: ; s5: upper byte of product ; s6: lower byte of product ; temp register: i ;=========================================================

Unsigned Multiplication Subroutine (2) mult_soft: load s5, 00 ;clear s5 load i, 08 ;initialize loop index mult_loop: sr0 s4 ;shift lsb to carry jump nc, shift_prod ;lsb is 0 add s5, s3 ;lsb is 1 shift_prod: sra s5 ;shift upper byte right, ;carry to MSB, LSB to carry sra s6 ;shift lower byte right, ;lsb of s5 to MSB of s6 sub i, 01 ;dec loop index jump nz, mult_loop ;repeat until i=0 return