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In order to realize the test bench, the parallel to serial converter of this post is used. PARALLEL TO SERIAL CONVERTER CODEIn Figure4 is reported a simulation of the serial to parallel converter VHDL code above. Serial to Parallel converter VHDL simulation resultsįigures below, the clock is set to 10 ns, so 80 ns mean 8 clock cycles. The output parallel data rate is slower than the input serial data rate, so noĮrror condition can occur. Parallel to serial converter in this case no error detection logic is present. Parallel data output and the relative enable pulse. P_serial2parallel : process(i_clk,i_rstb)Īn example of Serial to Parallel converterĬycles the counter enable the parallel output register and provides the Signal r_count : integer range 0 to G_N-1 Signal r_data : std_logic_vector(G_N-1 downto 0) O_data : out std_logic_vector(G_N-1 downto 0)) The parallel output to the module will be available every N clock cycle since N clock cycles are needed to load the shift register that provided the parallel output as in Figure2 Figure 2 Serial to Parallel conversion exampleĪn example of Serial to Parallel converter VHDL code Let assume the parallel data bus of the Serial to Parallel converter to be N bit. Serial to Parallel converter VHDL code example In other words, we will implement the VHDL block in the of the bottom right of Figure1 Figure 1 FPGA connection Parallel vs Serial ![]() PARALLEL TO SERIAL CONVERTER HOW TOWe will see how to implement the VHDL code for a serial to parallel interface in order to get back the parallel data bus we sent in the transmitter device. In this post, we want to implement the complementary interface of the parallel to serial interface. Many FPGA vendors like Xilinx, Intel/Altera give us the possibility to use internal serializer-deserializer such as a serial transceiver. This approach is very useful in interfacing different devices. PARALLEL TO SERIAL CONVERTER FULLBut I think the basic converters typically did their job without a full CPU - just a bunch of glue chips/logic to read a byte in one form and send it out as another.In this post, we analyzed the VHDL code for a parallel to serial converter. It seems that some manufacturers just never got serial handshaking to work well, and I sometimes had to resort to large buffers (typically a little box with a Z80 (or similar), 64k of RAM and ports for in & out) to work around the problem. Over the years, I found that parallel handshaking was very reliable but serial.not so much. ![]() Voltage is, I think, the least of the conversion issues. These have been available for a long time from Patton (sells nationwide but one of my favorites because they are nearby), B & B and Black Box - all of which still list parallel/serial converters on their web sites. PARALLEL TO SERIAL CONVERTER PLUSPlus end-to-end serial has big advantages over parallel - 200 feet without any problem at all. Plus there are situations (e.g., 6 terminals plus 2 printers all connected serial to an 8-port statistical multiplexer over a modem connection back to the host) where this is just simply not an option. With PC-compatibles this is trivial, but with other machines not always so easy. In more recent years I think they even had a network card that used the same interface slot, though I never bothered with that myself. There were (still are!) plenty of options: Add a port to the printerįor example, Okidata Microline printers would typically come standard with a parallel port but you could add a serial port card (I probably still have one around here somewhere). But there aren't so many printers these days with serial or parallel ports now that 100M (or even 1G) network ports for printers are dirt cheap, so we'll call it Retro. But ports for PCs are still available and as noted below, the companies I dealt with years ago for converters still sell them. Almost all the printers I use today (and most people I know) are connected USB or networked.
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