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Channel Tunnel

September 16th, 2022

I went for another walk along the Kent coast a few weeks ago, this time around the back of Folkestone near the Channel Tunnel and on to Dover.

Channel Tunnel terminal

I thought maybe I’d get a good view of the tunnel entrance from the hills above but it wasn’t as impressive as I’d imagined. Back when it first opened there was an exhibition centre somewhere around here but it must have been demolished.

A precipitous drop near Dover

The section of cliff-top path between Folkestone and Dover was awesome, I’ll give it 9/10 for walking experience. Dover itself doesn’t seem to have a lot worth visiting except the castle and the port. I dimly remember a family trip to the castle, but might warrant a repeat visit.

New NVC version 1.7

August 7th, 2022

I’ve just released another version of my VHDL simulator. The highlight of this release is greatly improved VHDL-2008 support. It’s now sufficiently complete to run OSVVM, UVVM, and NEORV32.

A special thank you to Brian Padalino and T. Meissner for sponsoring me!

Download: nvc-1.7.0.tar.gz

This release is signed with my PGP key ID 74319F1A: nvc-1.7.0.tar.gz.sig

  • Breaking change: In-tree builds are no longer supported: use a separate build directory instead.
  • Breaking change: The --force-init command is deprecated and has no effect.
  • Added support for VHDL-2008 type generics on packages and entities.
  • Diagnostic messages have been enhanced with more contextual information.
  • Added support for record element constraints and record fields with unconstrained array types.
  • Alias of multidimensional array allowed in VHDL-2008 mode.
  • Implemented VHDL-2008 rules for aggregates with slices.
  • VHPI is now always enabled at build time and the --enable-vhpi configure option has no effect.
  • Arithmetic operations that overflow the underlying machine type now produce an error (#101).
  • Added support for VHDL-2008 force/release assignments.
  • Basic support for external names in VHDL-2008.
  • Matching case case? statements are supported in VHDL-2008 mode.
  • Fixed several bugs in the implementation of guarded signals.
  • Implemented VHDL-2008 rules for generic visibility.
  • Shared variable declaration permitted in entity declaration.
  • Case expression no longer requires a locally static subtype in VHDL-2008 mode (#460).
  • The VHDL heap is now garbage collected as required by VHDL-2019 and the deallocate operator has no effect other than setting the access to null.
  • A new global option -H specifies the size of the simulation heap and defaults to 16 megabytes.
  • Concurrent procedure call allowed in entity statement part.
  • Added support for 'SUBTYPE and 'ELEMENT attributes in VHDL-2008.
  • The new top-level --init command creates a new empty library directory.
  • The -a analysis command now reads from the standard input if the file name is -.
  • Added support for array element constraints in VHDL-2008.
  • The --prefer-explicit analysis option which was deprecated before the 1.0 release has been removed.
  • A new --relaxed analysis option enables “relaxed rules” mode. This has the same effect as enabling all the existing --relax= options. However some constructs will still produce warnings.
  • The --relax= analysis option is deprecated and is now equivalent to passing --relaxed. The individual options are ignored.
  • Added support for generic subprograms in VHDL-2008.
  • New command --install allows easy installation of common third-party packages such as OSVVM and UVVM.
  • Identifiers in waveform dumps are now in lower case instead of upper case.
  • The function CURRENT_DELTA_CYCLE in NVC.SIM_PKG can be used to query the current delta cycle number.

Saltwood Castle

August 3rd, 2022

I went for a walk last weekend near Folkestone and to my surprise I discovered a castle!

It’s Saltwood castle and is, somewhat incredibly, someone’s private residence so you can’t go inside which is a shame.

Glynde to Eastbourne

July 22nd, 2022

A little walk I did recently along the South Downs Way near Eastbourne.

Nothing really remarkable happened but I got free tea and cake from a church (thanks Jesus!) and the scenery was nice. I missed these open chalk downlands.

Wind Farm

June 30th, 2022

As promised I went out to explore the nearby wind farm and in doing so made another crossing of the Romney marsh!

The place is called Little Cheyne Court wind farm and it was built in 2008 after a lot of local opposition. There’s a public footpath running right through it so you can get up really close to the turbines. It’s actually pretty scary standing underneath them with the blades spinning.

After that I plodded over the marsh to Dymchurch. Dymchurch is lovely! It’s a very stereotypical slightly-tacky British seaside resort, like a time capsule from the 60s or 70s. I had a 99 with a flake from an ice cream van, it was wonderful.

VHDL generic subprograms

June 25th, 2022

I recently added support for VHDL-2008 generic subprograms to NVC. As far as I know it’s the first open source VHDL simulator to support them and allows you to write type-generic functions and procedures like this:

function fact generic (type t;
                       function "*"(l, r : t) return t is <>;
                       function "-"(l, r : t) return t is <>;
                       function "<"(l, r : t) return boolean is <>;
                       one : t)
        (n : t) return t is
    if n < one then
        return one;
        return n * fact(n - one);
    end if;
end function;

And then make concrete instances of the generic function:

function fact_int is new fact
    generic map (t => integer, one => 1);
function fact_real is new fact
    generic map (t => real, one => 1.0);

The is <> syntax in the declaration above picks up the default *, -, and < operators for that type from the context so there’s no need to specify them in the generic map.

assert fact_int(5) = 120;
assert fact_real(4.0) = 24.0;

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North’s Seat

June 25th, 2022

The highest point in Hastings is called North’s Seat and is actually just behind my old secondary school. I walked up there a few weekends ago to have a look around.

The phone mast at the top

On the summit now there’s only this huge communications antenna but apparently there used to be a lookout post and a gibbet!

Some cow parsley (?) I saw on the way down

View across the Romney Marsh

In the distance we can see a wind farm: what else could be hidden there?! Stay tuned, I’m going to explore it tomorrow.

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Into The Marsh

May 30th, 2022

Last Friday was “Day of Care” at work so I decided to head out for an adventure to the wastelands of Romney Marsh.

The marsh is a large area of reclaimed land in Kent. As you might expect it’s very flat and perhaps not the most interesting terrain for walking.

Studying the map beforehand I knew I had to pay a visit to “Sheaty Sewer”, and this wooden bridge over a foetid open sewer vastly exceeded my expectations! (I think “sewer” might mean irrigation channel locally.)

Sheaty sewer

Below is the 800 year old church at St Mary in the Marsh. The church is open to look around during the day.

Church at St Mary in the Marsh

Towards the end I arrived at one of my favourite places, Dungeness! Not only is there a mini train and a lighthouse, there’s not one but two nuclear power plants! I discovered a path between them and the sea. It was very exciting. Below is Dungeness A, the older one, which is being decommissioned now but Dungeness B is still operating.

Dungeness A

Rye to Battle

May 26th, 2022

A somewhat uneventful walk from Rye to Battle, the site of the battle of Hastings no less. Here’s the river Tillingham just outside Rye.

One thing I’ve noticed down here is that footpaths are not nearly as well signposted as they were back up in Oxfordshire. I got lost quite often, including walking in a big circle at one point. Maybe my navigation just sucks now.

Bodium Castle and Robertsbridge

April 26th, 2022

Despite growing up here I’ve never done much exploring of the “interior” of East Sussex. Normally I just go for a walk along the coast in one direction of the other. Well, time to change that: a new programme of exploration is launched! The first mission is north to Bodium Castle and then to Robertsbridge.

A wood just outside Hastings

This was my favourite part of the walk, an unexpectedly lush wood just a few minutes from Hastings hospital.

Bodium Castle

Bodium Castle is basically what you get when you ask a five year old to draw a generic castle. It made a brief film appearance as “Swamp Castle” in Monty Python and the Holy Grail!

Robertsbridge high street

This was the most picturesque part of Robertsbridge, a small town on the Hastings-London train line. I’ve passed through it on the train loads of times but I don’t think this is the first time I’ve ventured into the town itself.

On the map I saw a “Robertsbridge Abbey” but what is left of the ruin is on private land and so a bit of a disappointment.