VHDL is a computer language which can be used to describe digital circuits. It has some similarity with software languages like C and basic (e.g. if/then/else structures, cases, loops etc.). There are also some important differences, e.g. processes which work in parallel and can communicate which each other by means of signals.
There are simulators to simulate digital circuits described in VHDL, and synthesizers to translate the VHDL into a netlist containing gates and flipflops.
1. VHDL of the HRPT decoder.
This decoder can handle:
- HRPT (NOAA)
- CHRPT (fengyun 1C, not operating anymore)
- Meteor N1
- Meteoa N2
Most important IO:
- usb interface
- elastic store
vhdl code decoder:
- clk: connect to external VCO
- phd: connect via LPF to regulating input of VCO
- sdi: split-phase input
- pd_ctrl: 12-bits output:
- (9 downto 0): 10-bits hrpt-data
- (10): '1' if first word of frame is present
- (11): sync state; '1'=inisync
- e_pd: '1' if new word available