The Channel Mapper

Introduction

ArC TWO does not have any concept of crosspoints, or wordlines and bitlines. It only exposes 64 channels that can be interconnected arbitrarily. The Channel Mapper is used to translate between ArC TWO channels and configurable crosspoints. Since there are many different requirements for channel configurations the mapping system is fully configurable to provide different ways to connect channels together. ArC2Control comes with a set of default mappers for common scenarios, but new mappers can be created. This is typically in the form of a simple TOML file that describes which channels are associated to specific bitlines or wordlines. For example this is mapping standard32.toml that’s included in ArC2Control installation.

[config]
# optional name for this configuration
# if left empty will default to the filename
name = "PLCC 32×32"
# number of total word- and bitlines (required)
words = 32
bits = 32
# optional list of masked crosspoints. If this
# key is set only the specified word/bitlines
# will be available in the crossbar view. This
# example enables every other crosspoint along
# the main diagonal
mask = [
  [ 0,  0], [ 2,  2], [ 4,  4], [ 6,  6],
  [ 8,  8], [10, 10], [12, 12], [14, 14],
  [16, 16], [18, 18], [20, 20], [22, 22],
  [24, 24], [26, 26], [28, 28], [30, 30]
]

[mapping]
# corresponding channels for wordlines
# in this case wordline 0 is channel 16, wordline 1 is channel 63
# and so on.
words = [
    16, 63, 17, 62, 18, 61, 19, 60,
    20, 59, 21, 58, 22, 57, 23, 56,
    24, 55, 25, 54, 26, 53, 27, 52,
    28, 51, 29, 50, 30, 49, 31, 48
]

# corresponding channels for bitlines
# in this case bitline 0 is channel 15, bitline 1 is channel 32
# and so on.
bits = [
    15, 32, 14, 33, 13, 34, 12, 35,
    11, 36, 10, 37,  9, 38,  8, 39,
     7, 40,  6, 41,  5, 42,  4, 43,
     3, 44,  2, 45,  1, 46,  0, 47
]

Using the mapper

Within the context of an ArC2Control session you should not need to instantiate mappers manually. The currently active mapper will always be available from the mapper property of the current module or long-running operation. Changes to the mapper are automatically propagated to modules. In order to do anything with ArC TWO you first need to convert the currently active crosspoint coordinates to the correct channel pair. This is usually done using the readonly wb2ch dict property that does the translation. For instance this is an abridged snippet from the curvetracer module that ships with ArC TWO.

def do_ramp(self, w, b, *args):

    # convert wordline w and bitline b to a corresponding (high/low)
    # ArC TWO channel pair
    (high, low) = self.mapper.wb2ch[w][b]

    # this can then be used to do ArC TWO operations
    # reminder: self.arc is always defined within modules
    self.arc.generate_ramp(high, low, *args)

Adding more mappings

ArC2Control comes with some standard mappings which are always available. Further mappings can be added in the local data directory, typically %APPDATA%\Roaming\arc2control\mappings in Windows, or ~/.local/share/arc2control/mappings on Linux. Files must end in .toml to be loaded properly during ArC2Control startup.

API Reference

class arc2control.mapper.ChannelMapper(nwords, nbits, wordarr, bitarr, mask, name)

ChannelMapper deals with conversions between word/bitlines and ArC2 channel numbers. ArC2 channels are arbitrary and can be operated independently. In a typical crossbar scenario some of these channels will be allocated to high potential terminals (wordlines) and others to low potential terminals (bitlines). This class provides convenience functions to switch back and forth.

The most typical way of loading a mapper would be through from_toml() to read the values from the configuration file, rather than create the objects manually.

Parameters:

nwords (int) – The number of wordlines
nbits (int) – The number of bitlines
wordarr – List of channels associated with wordlines 0 to nwords
bitarr – List of channels associated with bitlines 0 to nbits
name (str) – The name of this channel mapper

Returns:

A new ChannelMapper.

property b2ch: Get the corresponding channel, if any, for the specified bitline

property bit_idxs: Indices of the bit-associated channels in the ArC2 raw response. Typically libarc2 reports all channels, 0 to 63, in ascending channel order. This property will return the channels associated with bitlines in the current configuration in ascending bitline number order.

property ch2b: Get the corresponding bitline, if any, for the specified channel

property ch2w: Get the corresponding wordline, if any, for the specified channel

static from_toml(fname)

Create a new ChannelMapper from a toml configuration file. The mapper file MUST be UTF-8 encoded.

Parameters:: fname (str) – The filename of the mapper to load
Returns:: A new ChannelMapper.

property is_masked: Check if mapper has a crosspoint mask applied

property mask: Crossbar mask (available word-/bitlines)

property name: Returns the current configuration name

property nbits: Number of configured bitlines

property nwords: Number of configured wordlines

property total_devices: Total number of configured crosspoints.

property w2ch: Get the corresponding channel, if any, for the specified wordline

property wb2ch

Convert a (wordline, bitline) combination to a channel pair

>>> (high, low) = mapper.wb2ch[wordline][bitline]

property word_idxs: Indices of the word-associated channels in the ArC2 raw response. Typically libarc2 reports all channels, 0 to 63, in ascending channel order. This property will return the channels associated with wordlines in the current configuration in ascending wordline number order.