class MicroCisc::Vm::Device
This is a generic device base class providing memory and control access
From the docs, the control word layout is as follows:
-
0x0 -
Device
ID - read only. Unique system wide. -
0x1 - Local bank block (MSB) |
Device
type (LSB) - read only -
0x2 - Init device ID - read only if set, writable if 0 or by init device
-
0x3 - Accessed device block address (LSB) - writable by init device
-
0x4 - <Reserved> (MSB) |
Device
status (LSB) -
0x5 - Local register with interrupt handler address (read/write)
-
0x6 to 0xF -
Device
type specific (see below)
Constants
- TYPE_BLOCK_IO
- TYPE_BLOCK_MEMORY
- TYPE_HID
- TYPE_INVALID
- TYPE_PROCESSOR
- TYPE_SERIAL
- TYPE_TERMINAL
Attributes
id[R]
Public Class Methods
new(id, type, local_blocks, rom_blocks = [])
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# File lib/micro_cisc/vm/device.rb, line 25 def initialize(id, type, local_blocks, rom_blocks = []) @id = id @external_read = 0x003F @privileged_read = 0x003F @privileged_write = 0x002C @internal_write = 0x0010 @local_blocks = local_blocks rom_blocks.each { |block| block.freeze } ram_blocks = Array.new(local_blocks - rom_blocks.size).map do Array.new(256).map { 0 } end @local_mem = rom_blocks + ram_blocks @control = 0 @control_mem = Array.new(16).map { 0 } @control_mem[0] = id @control_mem[1] = type & 0xFF @control_mem[2] = 0 @devices = [self] end
Public Instance Methods
bank_index=(index)
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# File lib/micro_cisc/vm/device.rb, line 48 def bank_index=(index) @control_mem[1] = ((index & 0xFF) << 8) | (@control_mem[1] & 0xFF) end
banked?(address)
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# File lib/micro_cisc/vm/device.rb, line 96 def banked?(address) banked = ((address & 0xF000) >> 12) if banked == 0 banked = 1 else banked = 1 << banked end (banked & @control) != 0 end
devices=(devices)
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# File lib/micro_cisc/vm/device.rb, line 52 def devices=(devices) @devices = [self] + devices @devices.each_with_index { |device, index| device.bank_index = index } end
handle_control_read(address)
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# File lib/micro_cisc/vm/device.rb, line 88 def handle_control_read(address) # Does nothing by default, override in subclass end
handle_control_update(address, value)
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# File lib/micro_cisc/vm/device.rb, line 92 def handle_control_update(address, value) # Does nothing by default, override in subclass end
read_control(source_device_id, address)
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# File lib/micro_cisc/vm/device.rb, line 73 def read_control(source_device_id, address) if address == 0 handle_control_read(address) @control_mem[0] elsif source_device_id == @id || source_device_id == @control_mem[2] return 0 if (1 << (address - 1)) & @privileged_read == 0 handle_control_read(address) @control_mem[address] else return 0 if (1 << (address - 1)) & @external_read == 0 handle_control_read(address) @control_mem[address] end end
read_mem(source_device_id, address, force_local = false)
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# File lib/micro_cisc/vm/device.rb, line 128 def read_mem(source_device_id, address, force_local = false) banked = banked?(address) && !force_local device = (address >> 4) if banked && source_device_id == @id && device < @devices.size @devices[device].read_control(source_device_id, address & 0xF) elsif banked && source_device_id == @id && device >= 256 device = (address >> 8) if device < @devices.size @devices[device].read_mem(source_device_id, address & 0xFF) else page = (address & 0xFF00) >> 8 @local_mem[page][address & 0xFF] end elsif !banked && source_device_id == @id page = (address & 0xFF00) >> 8 @local_mem[page][address & 0xFF] elsif source_device_id == @control_mem[2] page = @control_mem[3] & 0xFF00 @local_mem[page][address * 0xFF] end end
write_control(source_device_id, address, value)
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# File lib/micro_cisc/vm/device.rb, line 57 def write_control(source_device_id, address, value) address = address & 0xF return if address == 0 if source_device_id == @id return if (1 << (address - 1)) & @internal_write == 0 @control_mem[address] = value elsif @control_mem[2] == 0 || source_device_id == @control_mem[2] # Special case where a processor can "claim" the device @control_mem[2] = source_device_id return if (1 << (address - 1)) & @privileged_write == 0 @control_mem[address] = value handle_control_update(address, value) end end
write_mem(source_device_id, address, value)
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# File lib/micro_cisc/vm/device.rb, line 106 def write_mem(source_device_id, address, value) banked = banked?(address) device = (address >> 4) if banked && source_device_id == @id && device < @devices.size @devices[device].write_control(source_device_id, address & 0xF, value) elsif banked && source_device_id == @id && device >= 256 device = (address >> 8) if device < @devices.size @devices[device].write_mem(source_device_id, address & 0xFF, value) else page = (address & 0xFF00) >> 8 @local_mem[page][address & 0xFF] = value end elsif !banked && source_device_id == @id block = (address & 0xFF00) >> 8 @local_mem[block][address & 0xFF] = value elsif source_device_id == @control_mem[2] block = @control_mem[3] @local_mem[block][address & 0xFF] = value if @local_mem[block] end end