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introduction std_logic_1164 gatelevel circuits delay models flipflops adders and arithm... counters LFSR and selftest memories programmable logic state-machine editor misc. demos I/O and displays DCF-77 clock relays (switch-le... CMOS circuits (sw...
RTLIB logic
input and ou... configuration animation incrementer adder subtraction rotate shifters comparison logic (bitwise) logic (wordw... muxes bit-twiddling bus-tap expand bits tri-state bu... RTLIB registers Prima processor D*CORE MicroJava Pic16 cosimulation Mips R3000 cosimu... Intel MCS4 (i4004) image processing ... [Sch04] Codeumsetzer [Sch04] Addierer [Sch04] Flipflops [Sch04] Schaltwerke [Sch04] RALU, Min... [Fer05] State-Mac... [Fer05] PIC16F84/... [Fer05] Miscellan... [Fer05] Femtojava FreeTTS
StdLogicVector and SignalStdLogicVector:
The RTLIB library is based on the same concept of multi-bit signals and operators as the VHDL std_logic_vector datatype. The current implementation relies on two main Java classes. While StdLogicVector (class hades.models.StdLogicVector) provides the basic data-type and most logical and arithmetic operations, SignalStdLogicVector (class hades.signals.SignalStdLogicVector) provides the corresponding signal type. Unlike the VHDL std_logic_vector data type, the current implementation of class StdLogicVector is limited to signals with up to 63 bits. (We use a very efficient internal representation based on long integers, which keeps the implementation simple and guarantees acceptable performance. Also, buses wider than 64 bits are seldom required for demonstrations. If necessary, the class could be rewritten to support wider buses.)The hades.models.rtlib package and its sub-packages hold the simulation components that operate on SignalStdLogicVector. The IpinVector component is used as the interactive switch to generate inputs values, while OpinVector is used to display the current signal values. Both IpinVector and OpinVector also act as hierarchy connectors that define the inputs and outputs of subdesigns in a design hierarchy.
Glow-mode:
If glow-mode is selected in the editor, the color of bit-vector signals is based on their current numerical value. The last digit of the decimal representation (i.e. value modulo 10) is used as an index to a table of ten different colors: 0=black, 1=brown, 2=red, 3=orange, 4=yellow, 5=green, 6=blue, 7=lilac, 8=gray, 9=dark blue-green. (Incidentally, these color are similar to the colors used to encode the values of resistors). The standard cyan, magenta, and orange colors are used for un-initialized (at least one 'U' bit), undefined (at least one 'X' bit), or tri-stated (all 'Z' bits) signals.
IpinVector usage:
- click an IpinVector to increment its current value
- shift+click an IpinVector to decrement its current value
- control+click an IpinVector to generate the special values ZZZ (all bits tristated), XXX (all bits undefined), and UUU (all bits un-initialized).
Open the IpinVector property-sheet dialog window to directly
enter a value numerically.
The parser understands decimal numbers as well as hexadecimal numbers
(written as cafe_H or 0xcafe)
and binary values (written as 00101100_b).
Enter the value and press the 'apply' or 'ok' buttons to
change the current output value of the IpinVector component.
You can also change the default number formatting (decimal, hex, binary)
via the IpinVector property-sheet.
In this applet, the upper IpinVector uses decimal formatting,
and the lower is set to hex formatting.
Clicking on an OpinVector will toggle its number formatting through the (decimal, hex, binary) states. For larger bit-widths, the default size of OpinVector is too small to fully contain the binary values (which results in redraw problems). The variant classes IpinVectorLarge and OpinVectorLarge (used three times in this applet) behave exactly like IpinVector and OpinVector, but use wider symbols that are better suited for the binary representation.