Lecture 13 PicoBlaze I/O & Interrupt Interface Example of Assembly Language Routine ECE 448 – FPGA and ASIC Design with VHDL

ECE 448 – FPGA and ASIC Design with VHDL Required reading P. Chu, FPGA Prototyping by VHDL Examples Chapter 16, PicoBlaze I/O Interface Chapter 17, PicoBlaze Interrupt Interface ECE 448 – FPGA and ASIC Design with VHDL

Output Decoding of Four Output Registers ECE 448 – FPGA and ASIC Design with VHDL

Timing Diagram of an Output Instruction ECE 448 – FPGA and ASIC Design with VHDL

Truth Table of a Decoding Circuit ECE 448 – FPGA and ASIC Design with VHDL

Block Diagram of Four Continuous-Access Ports ECE 448 – FPGA and ASIC Design with VHDL

Timing Diagram of an Input Instruction ECE 448 – FPGA and ASIC Design with VHDL

Block Diagram of Four Single-Access Ports ECE 448 – FPGA and ASIC Design with VHDL

ECE 448 – FPGA and ASIC Design with VHDL FIFO Interface clk rst clk rst FIFO din dout 8 8 full empty write read ECE 448 – FPGA and ASIC Design with VHDL

ECE 448 – FPGA and ASIC Design with VHDL Operation of FIFO ECE 448 – FPGA and ASIC Design with VHDL

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

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

ECE 448 – FPGA and ASIC Design with VHDL

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

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

Time-Multiplexed Seven Segment Display ECE 448 – FPGA and ASIC Design with VHDL

Block Diagram of the Hexadecimal Time-Multiplexing Circuit ECE 448 – FPGA and ASIC Design with VHDL

ECE 448 – FPGA and ASIC Design with VHDL Hexadecimal Multiplexing Circuit Based on PicoBlaze and mod-500 Counter ECE 448 – FPGA and ASIC Design with VHDL

Example of a function in the PicoBlaze assembly language ECE 448 – FPGA and ASIC Design with VHDL

Notation a Multiplicand ak-1ak-2 . . . a1 a0 x Multiplier xk-1xk-2 . . . x1 x0 p Product (a  x) p2k-1p2k-2 . . . p2 p1 p0

Multiplication of two 4-bit unsigned binary numbers Partial Product 0 Partial Product 1 Partial Product 2 Partial Product 3

Unsigned Multiplication – Basic Equations k-1 x =  xi  2i p = a  x i=0 k-1 p = a  x =  a  xi  2i = = x0a20 + x1a21 + x2a22 + … + xk-1a2k-1 i=0

Iterative Algorithm for Unsigned Multiplication Shift/Add Algorithm p = a  x = x0a20 + x1a21 + x2a22 + … + xk-1a2k-1 = = (...((0 + x0a2k)/2 + x1a2k)/2 + ... + xk-1a2k)/2 = k times p(0) = 0 p(j+1) = (p(j) + xj a 2k) / 2 j=0..k-1 p = p(k)

Unsigned Multiplication Computations 8 bits 8 bits pH pL p p(j) xj a + xj a 28 + pH pL C 2 p(j+1) >> 1 p(j+1) pH pL C pH = s5 pL = s6 PicoBlaze Registers 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 ; temporary register: ; s2: index j

Unsigned Multiplication Subroutine (2) mult_soft: load s5, 00 ;clear s5 load s2, 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 s2, 01 ;dec loop index jump nz, mult_loop ;repeat until i=0 return

Edit instructions - Shifts *All shift instructions affect Zero and Carry flags