#Vhdl program for left shift register manuals
#Vhdl program for left shift register serial
#Vhdl program for left shift register software
#Vhdl program for left shift register code
#Vhdl program for left shift register simulator

In VHDL, this is called signal scheduling. 'Theoretically something like this should show the outputs q to be the same as input d' However I have some suggestions in your code.ġ) Process needs only clk and rst in the sensitive list, as the rest are synchronous signals as per your code. There are known issues between these two constructs in some simulators. Check rising_edge(clk) instead of clk=1 clk'event.

#Vhdl program for left shift register simulator

Your simulator is never entering into your clock block. So it seems like it is a simulator issue here or mistake in the way you simulated this design. It gave the expected waveforms as per your code. I checked this in modelsim 6.5, 10.4 and iSim 14.7. I cannot find a fix for this or infact all the modes (s= 00, 01, 10, 11) show no changes in the output. Theoretically something like this should show the outputs q to be the same as input d Therefore the signal temp is assigned with input d and then the output q is assigned the signal temp. I tried running this on Xilinx ISE simulator but when I simulate the waveform, there seems to be no changes to the outputs.Īs the image above shows, when s = '11', the outputs q should be the same as the inputs d as when '11' => Signal temp: std_logic_vector(3 downto 0)

#Vhdl program for left shift register code

I have managed to write the code which from reviewing it a couple of times, seems without errors (I understand sometimes the code can compile successfully but in fact there would be a few problems in there which aren't so obvious).

#Vhdl program for left shift register software

I am also using Xilinx software to simulate the VHDL code.

#Vhdl program for left shift register serial

The following table shows pin definitions for an 8-bit shift-left register with a positive-edge clock, synchronous set, serial in, and serial out.įollowing is VHDL code for an 8-bit shift-left register with a positive-edge clock, asynchronous parallel load, serial in, and serial out.įollowing is the Verilog code for an 8-bit shift-left register with a positive-edge clock, asynchronous parallel load, serial in, and serial out.Įndmodule 8-bit Shift-Left Register with Positive-Edge Clock, Synchronous Parallel Load, Serial In, and Serial Outįollowing is the VHDL code for an 8-bit shift-left register with a positive-edge clock, synchronous parallel load, serial in, and serial out.įollowing is the Verilog code for an 8-bit shift-left register with a positive-edge clock, synchronous parallel load, serial in, and serial out.I am designing a universal shift register of 4 bits in VHDL. Note Because this example includes an asynchronous clear XST will not infer SRL16. The following table shows pin definitions for an 8-bit shift-left register with a negative-edge clock, clock enable, serial in, and serial out.įollowing is the VHDL code for an 8-bit shift-left register with a positive-edge clock, asynchronous clear, serial in, and serial out.įollowing is the Verilog code for an 8-bit shift-left register with a positive-edge clock, asynchronous clear, serial in, and serial out.Įndmodule 8-bit Shift-Left Register with Positive-Edge Clock, Synchronous Set, Serial In, and Serial Out Note For this example, XST will infer SRL16E_1. Signal tmp: std_logic_vector(7 downto 0) įollowing is the Verilog code for an 8-bit shift-left register with a positive-edge clock, serial in, and serial out.Įndmodule 8-bit Shift-Left Register with Negative-Edge Clock, Clock Enable, Serial In, and Serial Out The following figure shows the pin layout of SRL16E.įollowing is the VHDL code for an 8-bit shift-left register with a positive-edge clock, serial in, and serial out. Both are available with or without a clock enable.

#Vhdl program for left shift register manuals

Ĭonsult the VHDL/Verilog language reference manuals for more information.īefore writing Shift Register behavior it is important to recall that Virtex, Virtex-E, Virtex-II, and Virtex-II Pro have specific hardware resources to implement Shift Registers: SRL16 for Virtex and Virtex-E, and SRLC16 for Virtex-II and Virtex-II Pro.

predefined shift operators for example, sll, srl.

There are different ways to describe shift registers.

parallel: the contents of one or several of flip-flops other than the last one, is accessed.

serial: only the contents of the last flip-flop is accessed by the rest of the circuit.

In general a shift register is characterized by the following control and data signals, which are fully recognized by XST: