Parity
generator
Task: Design a circuit for generating a parity bit
for 8-bit input word. The 8-bit input word should be set by means of switches SW0-SW7
on the prototype board. Parity should be presented on the LED display: E
- even number of ‘ones’ in the 8-bit input word, O - odd number of ones.
Fig. 1.
Photograph of the Digilent Spartan 3 board.
Perform a functional simulation and verify the circuit practically by
programming the prototype board. On the prototype board there are 4
seven-segment displays with common anode connected for multiplexed operation.
Present the result on the AN3 display. The multiplexed connection is
made by a common connection of all segment leads, ie, the common connection of
segments A of 4 displays, the common connection of segments B of
4 displays, etc. Common anodes are used to activate a given digit. Individual
segments of an active digit are activated by a low logic state on the A-G
leads. The activation of the individual digits is triggered by the low
logic state on the AN0 - AN3 (inverted common anode) pins.
For example, if you want to suppress the digits 0-2, then you must set
logic ‘1’ at the AN0 - AN2 terminals. If at the same time you want to
display the sign ‘A’ on the digit 3 then assert the following signals: AN3='0'
and A='0', B='0', C='0', D='1',
E='0', F='0', G='0', DP='1'.
Fig. 2. Connections of segments and digits of LED
display. Example of displaying digit '2'.
UCF file for the exercise,
Digilent Spartan-3 board, Spartan-3 3S200 FT256-4:
#################################################################
# Seven-segment LED display:
NET "led7_an_o<3>" LOC = "E13" ; # leftmost digit,
active low
NET "led7_an_o<2>" LOC = "F14" ; # active low
NET "led7_an_o<1>" LOC = "G14" ; # active low
NET "led7_an_o<0>" LOC = "D14" ; # rightmost digit,
active low
#
NET "led7_seg_o<7>" LOC = "E14" ; # segment 'A',
active low
NET "led7_seg_o<6>" LOC = "G13" ; # segment 'B',
active low
NET "led7_seg_o<5>" LOC = "N15" ; # segment 'C',
active low
NET "led7_seg_o<4>" LOC = "P15" ; # segment 'D',
active low
NET "led7_seg_o<3>" LOC = "R16" ; # segment 'E',
active low
NET "led7_seg_o<2>" LOC = "F13" ; # segment 'F',
active low
NET "led7_seg_o<1>" LOC = "N16" ; # segment 'G',
active low
NET "led7_seg_o<0>" LOC = "P16" ; # segment 'dp',
active low
#################################################################
#################################################################
# Slide switches:
# sw7 sw6 sw5 sw4 sw3 sw2 sw1 sw0
NET "sw_i<0>" LOC = "F12" ; # active high when in UP
position
NET "sw_i<1>" LOC = "G12" ; # active high when in UP
position
NET "sw_i<2>" LOC = "H14" ; # active high when in UP
position
NET "sw_i<3>" LOC = "H13" ; # active high when in UP
position
NET "sw_i<4>" LOC = "J14" ; # active high when in UP
position
NET "sw_i<5>" LOC = "J13" ; # active high when in UP
position
NET "sw_i<6>" LOC = "K14" ; # active high when in UP
position
NET "sw_i<7>" LOC = "K13" ; # active high when in UP
position
#################################################################