Class: Origen::Registers::Bit

Inherits:
Object
  • Object
show all
Defined in:
lib/origen/registers/bit.rb

Overview

Models bits within Reg objects

Constant Summary collapse

ACCESS_CODES =

The :access property of registers or bits can be set to any of the following key values. Implemented refers to whether the behaviour is accurately modelled by the Origen register model or not.

{
  ro:    { implemented: false, description: 'Read-Only' },
  rw:    { implemented: true,  description: 'Read-Write' },
  rc:    { implemented: false, description: 'Read-only, Clear-on-read' },
  rs:    { implemented: false, description: "Set-on-read (all bits become '1' on read)" },
  wrc:   { implemented: false, description: 'Writable, clear-on-read' },
  wrs:   { implemented: false, description: 'Writable, Sets-on-read' },
  wc:    { implemented: false, description: 'Clear-on-write' },
  ws:    { implemented: false, description: 'Set-on-write' },
  wsrc:  { implemented: false, description: 'Set-on-write, clear-on-read' },
  wcrs:  { implemented: false, description: 'Clear-on-write, set-on-read' },
  w1c:   { implemented: false, description: "Write '1' to clear bits" },
  w1s:   { implemented: false, description: "Write '1' to set bits" },
  w1t:   { implemented: false, description: "Write '1' to toggle bits" },
  w0c:   { implemented: false, description: "Write '0' to clear bits" },
  w0s:   { implemented: false, description: "Write '0' to set bits" },
  w0t:   { implemented: false, description: "Write '0' to toggle bits" },
  w1src: { implemented: false, description: "Write '1' to set and clear-on-read" },
  w1crs: { implemented: false, description: "Write '1' to clear and set-on-read" },
  w0src: { implemented: false, description: "Write '0' to set and clear-on-read" },
  w0crs: { implemented: false, description: "Write '0' to clear and set-on-read" },
  wo:    { implemented: false, description: 'Write-only' },
  woc:   { implemented: false, description: "When written sets the field to '0'. Read undeterministic" },
  worz:  { implemented: false, description: 'Write-only, Reads zero' },
  wos:   { implemented: false, description: "When written sets all bits to '1'. Read undeterministic" },
  w1:    { implemented: false, description: 'Write-once. Next time onwards, write is ignored. Read returns the value' },
  wo1:   { implemented: false, description: 'Write-once. Next time onwards, write is ignored. Read is undeterministic' },
  dc:    { implemented: false, description: 'RW but no check' },
  rowz:  { implemented: false, description: 'Read-only, value is cleared on read' }
}

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(owner, position, options = {}) ⇒ Bit

rubocop:disable MethodLength



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# File 'lib/origen/registers/bit.rb', line 88

def initialize(owner, position, options = {}) # rubocop:disable MethodLength
  options = {
    start:                   false,        # whether bit starts a state machine so be careful
    read_data_matches_write: true,
    read:                    false,
    overlay:                 false,
    store:                   false,
    sticky_overlay:          true,
    sticky_store:            false,
    nvm_dep:                 false,        # whether is an NVM dependent bit
  }.merge(options)
  @owner = owner
  @position = position
  @undefined = options.delete(:undefined)
  @reset_val = (options.delete(:res) || options.delete(:reset) || options.delete(:data) || 0)
  if @reset_val.is_a?(Symbol)
    @data = 0
  else
    @reset_val &= 1 unless @reset_val.is_a?(Symbol)
    @data = @reset_val
  end

  access_code = options.delete(:access)
  # If access has been defined then none of these other attributes can be
  if access_code
    conflicts = [:readable, :writable, :clr_only, :set_only, :w1c]
    if conflicts.any? { |k| options.key?(k) }
      puts 'The following attributes cannot be set in combination with :access'
      puts "  #{conflicts.join(', ')}"
      puts ''
      puts 'Use :access to defined the required behavior, the above attributes will be deprecated in future.'
      puts ''
      fail 'Conflicting access!'
    end
    set_access(access_code)
  else
    options = {
      writable: true,         # whether bit is writable
      readable: true,         # whether bit is readable
      clr_only: false,        # whether bit is clear only
      set_only: false,        # whether bit is set only
      w1c:      false,        # whether bit is w1c (when written to 1 immediately becomes 0)
    }.merge(options)
    @readable = options.delete(:readable)
    @writable = options.delete(:writable)
    @clr_only = options.delete(:clr_only)
    @set_only = options.delete(:set_only)
    @w1c = options.delete(:w1c)
    set_access_from_rw
  end
  # Would like to get this integrated with access as well
  @read_data_matches_write = options.delete(:read_data_matches_write)

  @feature = options.delete(:feature)
  if !!feature && @writable
    @writable = enabled?
  end
  @path     = options.delete(:path)
  @abs_path = options.delete(:abs_path)
  @start = options.delete(:start)
  @read = options.delete(:read)
  @overlay = options.delete(:overlay)
  @store = options.delete(:store)
  @update_required = false
  @sticky_store = options.delete(:sticky_store)
  @sticky_overlay = options.delete(:sticky_overlay)
  @nvm_dep = (options.delete(:nvm_dep) ? 1 : 0)
  # Delete some other noise that can be left over...
  options.delete(:bits)
  options.delete(:pos)
  options.delete(:position)
  options.delete(:data)
  # Whatever is left must be custom application meta-data
  @meta = (default_bit_metadata).merge(options)
end

Dynamic Method Handling

This class handles dynamic methods through the method_missing method

#method_missing(method, *args, &block) ⇒ Object

:nodoc:



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# File 'lib/origen/registers/bit.rb', line 475

def method_missing(method, *args, &block) # :nodoc:
  if meta_data_method?(method)
    extract_meta_data(method, *args)
  else
    super
  end
end

Instance Attribute Details

#access ⇒ Object

Returns the access method for the given bit (a symbol), see the ACCESS_CODES constant for the possible values this can have and their meaning



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# File 'lib/origen/registers/bit.rb', line 86

def access
  @access
end

#clr_only=(value) ⇒ Object (writeonly)

Allow modify of clr_only flag, bit can only be cleared (made 0)



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# File 'lib/origen/registers/bit.rb', line 72

def clr_only=(value)
  @clr_only = value
end

#data ⇒ Object (readonly)

Current the data value currently held by the bit, 0 or 1



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# File 'lib/origen/registers/bit.rb', line 44

def data
  @data
end

#feature ⇒ Object (readonly)

Any feature associated with the bit/bits



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# File 'lib/origen/registers/bit.rb', line 60

def feature
  @feature
end

#meta ⇒ Object Also known as: meta_data, metadata

Returns any application-specific meta-data attatched to the given bit



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# File 'lib/origen/registers/bit.rb', line 81

def meta
  @meta
end

#nvm_dep ⇒ Object (readonly)

Returns true if bit depends on initial state of NVM in some way



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# File 'lib/origen/registers/bit.rb', line 76

def nvm_dep
  @nvm_dep
end

#overlay(value) ⇒ Object (readonly)

Set the overlay attribute to the supplied value



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# File 'lib/origen/registers/bit.rb', line 46

def overlay
  @overlay
end

#owner ⇒ Object (readonly)

Returns the Reg object that owns the bit



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# File 'lib/origen/registers/bit.rb', line 40

def owner
  @owner
end

#position ⇒ Object (readonly)

Returns the integer position of the bit within the register



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# File 'lib/origen/registers/bit.rb', line 42

def position
  @position
end

#read_data_matches_write ⇒ Object (readonly)

If the bit does not read back with the same data as is written to it then this will return true. This property can be assigned durgin the register instantiation, e.g.

add_reg :control,    0x00,    :mode    => { :pos => 8, :bits => 8 },
                              :status  => { :pos => 4, :bits => 2, :read_data_matches_write => false }



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# File 'lib/origen/registers/bit.rb', line 52

def read_data_matches_write
  @read_data_matches_write
end

#readable=(value) ⇒ Object (writeonly)

Allow modify of readable flag, bit is readable by read method



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# File 'lib/origen/registers/bit.rb', line 68

def readable=(value)
  @readable = value
end

#reset_val ⇒ Object Also known as: reset_data, reset_value

Returns the reset value of the bit



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# File 'lib/origen/registers/bit.rb', line 62

def reset_val
  @reset_val
end

#set_only=(value) ⇒ Object (writeonly)

Allow modify of set_only flag, bit can only be set (made 1)



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# File 'lib/origen/registers/bit.rb', line 74

def set_only=(value)
  @set_only = value
end

#start ⇒ Object (readonly)

Returns true if bit is critical to starting an important operation (like a state machine) so that it can be made not writable during basic register checks



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# File 'lib/origen/registers/bit.rb', line 79

def start
  @start
end

#sticky_overlay ⇒ Object

Returns true if this bit has the sticky_overlay flag set, see Reg#sticky_overlay for a full description. This is true by default.



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# File 'lib/origen/registers/bit.rb', line 55

def sticky_overlay
  @sticky_overlay
end

#sticky_store ⇒ Object

Returns true if this bit has the sticky_store flag set, see Reg#sticky_store for a full description. This is false by default.



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# File 'lib/origen/registers/bit.rb', line 58

def sticky_store
  @sticky_store
end

#w1c ⇒ Object

Sets or returns the status of “write-one-to-clear”



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# File 'lib/origen/registers/bit.rb', line 70

def w1c
  @w1c
end

#writable=(value) ⇒ Object (writeonly)

Allow modify of writable flag, bit is writeable by write method



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# File 'lib/origen/registers/bit.rb', line 66

def writable=(value)
  @writable = value
end

Class Method Details

.null(owner, position) ⇒ Object

Returns a ‘null’ bit object which has value 0 and no other attributes set



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# File 'lib/origen/registers/bit.rb', line 403

def self.null(owner, position) # :nodoc:
  Bit.new(owner, position, writable: false)
end

Instance Method Details

#abs_path ⇒ Object 



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# File 'lib/origen/registers/bit.rb', line 222

def abs_path
  @abs_path
end

#clear_flags ⇒ Object

Clears the read, store, overlay and update_required flags of this bit. The store and overlay flags will not be cleared if the the bit’s sticky_store or sticky_overlay attributes are set respectively.



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# File 'lib/origen/registers/bit.rb', line 380

def clear_flags
  @read = false
  @store = false unless @sticky_store
  @overlay = false unless @sticky_overlay
  @update_required = false
  self
end

#clear_read_flag ⇒ Object

Clears the read flag of this bit.



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# File 'lib/origen/registers/bit.rb', line 389

def clear_read_flag
  @read = false
  self
end

#clear_start ⇒ Object

Clears any start bits that are set



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# File 'lib/origen/registers/bit.rb', line 440

def clear_start
  if @start && set?
    @data = 0
  end
  self
end

#clear_w1c ⇒ Object

Clears any w1c bits that are set



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# File 'lib/origen/registers/bit.rb', line 432

def clear_w1c
  if @w1c && set?
    @data = 0
  end
  self
end

#data_in_position ⇒ Object

Returns the data shifted by the bit position



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# File 'lib/origen/registers/bit.rb', line 427

def data_in_position
  data << position
end

#default_bit_metadata ⇒ Object

Returns any application specific metadata that has been inherited by the given bit. This does not account for any overridding that may have been applied to this bit specifically however, use the meta method to get that.



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# File 'lib/origen/registers/bit.rb', line 236

def default_bit_metadata
  if owner
    Origen::Registers.default_bit_metadata.merge(
      Origen::Registers.bit_metadata[owner.owner.class] || {})
  else
    Origen::Registers.default_bit_metadata
  end
end

#delete ⇒ Object

Make this bit disappear, make it unwritable with a data value of 0



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# File 'lib/origen/registers/bit.rb', line 255

def delete
  @sticky_overlay = false
  @sticky_store = false
  clear_flags
  @data = 0
  @writable = false
  self
end

#enabled? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/origen/registers/bit.rb', line 502

def enabled?
  if feature
    value = false
    current_owner = self
    if feature.class == Array
      feature.each do |f|
        current_owner = self
        loop do
          if current_owner.respond_to?(:owner)
            current_owner = current_owner.owner
            if current_owner.respond_to?(:has_feature?)
              if current_owner.has_feature?(f)
                value = true
                break
              end
            end
          else # if current owner does not have a owner
            value = false
            break
          end
        end # loop end
        unless value
          if Origen.top_level && \
             Origen.top_level.respond_to?(:has_feature?) && \
             Origen.top_level.has_feature?(f)
            value = true
            unless value
              break
            end
          end
        end
        unless value
          break # break if feature not found and return false
        end
      end # iterated through all features in array
      return value
    else # if feature.class != Array
      loop do
        if current_owner.respond_to?(:owner)
          current_owner = current_owner.owner
          if current_owner.respond_to?(:has_feature?)
            if current_owner.has_feature?(feature)
              value = true
              break
            end
          end
        else # if current owner does not have a owner
          value = false
          break
        end
      end # loop end
      unless value
        if Origen.top_level && \
           Origen.top_level.respond_to?(:has_feature?) && \
           Origen.top_level.has_feature?(feature)
          value = true
        end
      end
      return value
    end
  else
    return true
  end
end

#enabled_by_feature?(name = nil) ⇒ Boolean Also known as: has_feature_constraint?

Returns true if the bit is constrained by the given/any feature

Returns:

  • (Boolean) 


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# File 'lib/origen/registers/bit.rb', line 484

def enabled_by_feature?(name = nil)
  if !name
    !!feature
  else
    if feature.class == Array
      feature.each do |f|
        if f == name
          return true
        end
      end
      return false
    else
      feature == name
    end
  end
end

#extract_meta_data(method, *args) ⇒ Object 



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# File 'lib/origen/registers/bit.rb', line 466

def extract_meta_data(method, *args)
  method = method.to_s.sub('?', '')
  if method =~ /=/
    instance_variable_set("@#{method.sub('=', '')}", args.first)
  else
    instance_variable_get("@#{method}") || meta[method.to_sym]
  end
end

#has_known_value? ⇒ Boolean

Returns true if the value of the bit is known. The value will be unknown in cases where the reset value is undefined or determined by a memory location and where the bit has not been written or read to a specific value yet.

Returns:

  • (Boolean) 


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# File 'lib/origen/registers/bit.rb', line 290

def has_known_value?
  !@reset_val.is_a?(Symbol) || @updated_post_reset
end

#has_overlay?(name = nil) ⇒ Boolean

Returns true if the overlay attribute is set, optionally supply an overlay name and this will only return true if the overlay attribute matches that name

Returns:

  • (Boolean) 


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# File 'lib/origen/registers/bit.rb', line 358

def has_overlay?(name = nil)
  if name
    name.to_s == @overlay.to_s
  else
    !!@overlay
  end
end

#inspect ⇒ Object 



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# File 'lib/origen/registers/bit.rb', line 245

def inspect
  "<#{self.class}:#{object_id}>"
end

#is_readable? ⇒ Boolean Also known as: readable?

Returns:

  • (Boolean) 


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# File 'lib/origen/registers/bit.rb', line 372

def is_readable?
  @readable
end

#is_to_be_read? ⇒ Boolean

Returns true if the bit’s read flag is set

Returns:

  • (Boolean) 


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# File 'lib/origen/registers/bit.rb', line 347

def is_to_be_read?
  @read
end

#is_to_be_stored? ⇒ Boolean

Returns true if the bit’s store flag is set

Returns:

  • (Boolean) 


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# File 'lib/origen/registers/bit.rb', line 352

def is_to_be_stored?
  @store
end

#is_writable? ⇒ Boolean Also known as: writable?

Returns true if the bit is writable

Returns:

  • (Boolean) 


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# File 'lib/origen/registers/bit.rb', line 367

def is_writable?
  @writable
end

#mask ⇒ Object

Returns a bit mask for this bit, that is a 1 shifted into the position corresponding to this bit’s position. e.g. A bit with position 4 would return %1_0000



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# File 'lib/origen/registers/bit.rb', line 397

def mask
  mask_val = 1
  mask_val << @position
end

#meta_data_method?(method) ⇒ Boolean

This method is part of a private API. You should avoid using this method if possible, as it may be removed or be changed in the future.

Returns:

  • (Boolean) 


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# File 'lib/origen/registers/bit.rb', line 453

def meta_data_method?(method)
  attr_name = method.to_s.gsub(/\??=?/, '').to_sym
  if default_bit_metadata.key?(attr_name)
    if method.to_s =~ /\?/
      [true, false].include?(default_bit_metadata[attr_name])
    else
      true
    end
  else
    false
  end
end

#overlay_str ⇒ Object

Returns the overlay attribute



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# File 'lib/origen/registers/bit.rb', line 342

def overlay_str
  @overlay
end

#path_var ⇒ Object 



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# File 'lib/origen/registers/bit.rb', line 218

def path_var
  @path
end

#read(value = nil, _options = {}) ⇒ Object Also known as: assert

Will tag all bits for read and if a data value is supplied it will update the expected data for when the read is performed.



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# File 'lib/origen/registers/bit.rb', line 317

def read(value = nil, _options = {})
  # First properly assign the args if value is absent...
  if value.is_a?(Hash)
    options = value
    value = nil
  end
  write(value) if value
  @read = true if @readable && @read_data_matches_write
  self
end

#reset ⇒ Object

Resets the data value back to the reset value and calls Bit#clear_flags



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# File 'lib/origen/registers/bit.rb', line 270

def reset
  if @reset_val.is_a?(Symbol)
    @data = 0
  else
    @data = @reset_val
  end
  @updated_post_reset = false
  clear_flags
  self
end

#respond_to?(*args) ⇒ Boolean

:nodoc:

Returns:

  • (Boolean) 


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# File 'lib/origen/registers/bit.rb', line 447

def respond_to?(*args) # :nodoc:
  sym = args.first
  meta_data_method?(sym) || super(sym)
end

#set? ⇒ Boolean

Returns true if the bit is set (holds a data value of 1)

Returns:

  • (Boolean) 


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# File 'lib/origen/registers/bit.rb', line 265

def set?
  @data == 1 ? true : false
end

#set_access(value) ⇒ Object 



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# File 'lib/origen/registers/bit.rb', line 164

def set_access(value)
  unless ACCESS_CODES.keys.include?(value)
    puts 'Invalid access code, must be one of these:'
    ACCESS_CODES.each do |code, meta|
      puts "  :#{code}".ljust(10) + " - #{meta[:description]}"
    end
    puts ''
    fail 'Invalid access code!'
  end
  @access = value

  # Set readable & writable based on access
  if @access == :ro
    @readable = true
    @writable = false
  elsif @access == :wo || @access == :worz
    @writable = true
    @readable = false
  elsif @access == :w1c
    @w1c = true
    @writable = true
    @readable = true  # Is this always valid?
  elsif @access == :wc
    @clr_only = true
    @writable = true
    @readable = true  # Is this always valid?
  elsif @access == :ws
    @set_only = true
    @writable = true
    @readable = true  # Is this always valid?
  # Catch all for now until the behavior of this class is based around @access
  else
    @writable = true
    @readable = true
  end
end

#set_access_from_rw ⇒ Object

Set @access based on @readable and @writable



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# File 'lib/origen/registers/bit.rb', line 202

def set_access_from_rw
  if @w1c
    @access = :w1c
  elsif @clr_only
    @access = :wc
  elsif @set_only
    @access = :ws
  elsif @readable && @writable
    @access = :rw
  elsif @readable
    @access = :ro
  elsif @writable && @access != :worz
    @access = :wo
  end
end

#setting(value) ⇒ Object

Returns the value you would need to write to the register to put the given value in this bit



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# File 'lib/origen/registers/bit.rb', line 409

def setting(value)
  value = value & 1   # As this bit can only hold one bit of data force it
  value << @position
end

#shift_out_left {|_self| ... } ⇒ Object

With only one bit it just returns itself

Yields:

  • (_self)

Yield Parameters:



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# File 'lib/origen/registers/bit.rb', line 422

def shift_out_left
  yield self
end

#size ⇒ Object

Always returns 1 when asked for size, a BitCollection on the other hand will return something higher



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# File 'lib/origen/registers/bit.rb', line 250

def size
  1
end

#store ⇒ Object

Sets the store flag attribute



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# File 'lib/origen/registers/bit.rb', line 330

def store
  @store = true
  self
end

#undefined? ⇒ Boolean

Returns true if the bit object is a placeholder for bit positions that have not been defined within the parent register

Returns:

  • (Boolean) 


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# File 'lib/origen/registers/bit.rb', line 283

def undefined?
  @undefined
end

#update_required? ⇒ Boolean

Returns true if the bit’s update_required flag is set, typically this will be the case when a write has changed the data value of the bit but a BitCollection#write! method has not been called yet to apply it to silicon

Returns:

  • (Boolean) 


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# File 'lib/origen/registers/bit.rb', line 417

def update_required?
  @update_required
end

#write(value, options = {}) ⇒ Object

Set the data value of the bit to the given value (1 or 0) If the bit is read-only, the value of the bit can be forced with ‘force: true’



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# File 'lib/origen/registers/bit.rb', line 296

def write(value, options = {})
  # If an array is written it means a data value and an overlay have been supplied
  # in one go...
  if value.is_a?(Array)
    overlay(value[1])
    value = value[0]
  end
  if (@data != value & 1 && @writable) ||
     (@data != value & 1 && options[:force] == true)
    if ((set?) && (!@set_only)) ||
       ((!set?) && (!@clr_only))
      @data = value & 1
      @update_required = true
      @updated_post_reset = true
    end
  end
  self
end