Transcript ECE 545—Introduction to VHDL Lecture 9

Lecture 13
PicoBlaze I/O & Interrupt Interface
Example of
Assembly Language Routine
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
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Output Decoding of Four Output Registers
ECE 448 – FPGA and ASIC Design with VHDL
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Timing Diagram of an Output Instruction
ECE 448 – FPGA and ASIC Design with VHDL
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Truth Table of a Decoding Circuit
ECE 448 – FPGA and ASIC Design with VHDL
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Block Diagram of Four Continuous-Access Ports
ECE 448 – FPGA and ASIC Design with VHDL
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Timing Diagram of an Input Instruction
ECE 448 – FPGA and ASIC Design with VHDL
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Block Diagram of Four Single-Access Ports
ECE 448 – FPGA and ASIC Design with VHDL
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FIFO Interface
clk
rst
clk
rst
FIFO
din
dout
8
8
full
write
empty
read
ECE 448 – FPGA and ASIC Design with VHDL
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Operation of FIFO
ECE 448 – FPGA and ASIC Design with VHDL
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Interrupt
Flow
ECE 448 – FPGA and ASIC Design with VHDL
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Timing Diagram of an Interrupt Event
ECE 448 – FPGA and ASIC Design with VHDL
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ECE 448 – FPGA and ASIC Design with VHDL
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Interrupt Interface with a Single Event
ECE 448 – FPGA and ASIC Design with VHDL
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Interrupt Interface with Two Requests
ECE 448 – FPGA and ASIC Design with VHDL
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Time-Multiplexed Seven Segment Display
ECE 448 – FPGA and ASIC Design with VHDL
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Block Diagram of the Hexadecimal
Time-Multiplexing Circuit
ECE 448 – FPGA and ASIC Design with VHDL
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Hexadecimal Multiplexing Circuit Based on
PicoBlaze and mod-500 Counter
ECE 448 – FPGA and ASIC Design with VHDL
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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 =  x i  2i
p=ax
i=0
k-1
p = a  x =  a  x i  2i =
i=0
= x0a20 + x1a21 + x2a22 + … + xk-1a2k-1
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
pL
pH
xj a
+
pL
>> 1
C
p(j)
+ xj a 28
pH
C
p
pL
pH
pH = s5
pL = s6
a = s3
x = s4
2 p(j+1)
p(j+1)
PicoBlaze Registers
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