
15.16 Digital Systems: Principles and Design
Solution
1. type logicStateDecoder is (‘0’, ‘1’, ‘Z’);
2. (i) type supplyVoltage is range 1 to 2000
units
mV;
V = 1000 milliV;
kV = 1000 V;
end units
(ii) type CMOS_voltage is range −12.0 to 12.0;
3. signal A, B, D : std_logic; -- The signals A, B and D are of the std_logic type
of data.
4. (i) type std_ulogic is (‘U’, ‘X ’, ‘0’, ‘1’, ‘Z’, ‘W’, ‘L’, ‘H ’, ‘_’);
(ii) subtype xorlogic is std_ulogic range ‘0’ to ‘1’;
Points to Remember
1. Each data object can have a value which is from a set of values.
2. Each data type defines a set of values.
3. Each data type also defines a set of permitted operations.