def assert_read(address, value, error_msg='wrong data read'):
dut.i_address = address
dut.i_read_enable = 1
yield from wait()
assert_io_data(value, error_msg)
dut.i_read_enable = 0
yield from wait()
def memory_address_register(dut):
def assert_o_address(value, error_msg):
"""Check the output address"""
assertions.assertEqual(dut.o_address.value.binstr, value, error_msg)
# Test initialization
yield from wait()
assert_o_address('0000', 'Address should initialize to 0000')
dut.i_reset = 0
# Set the input address to store
dut.i_address = 0b0100
yield from wait()
assert_o_address('0000', 'Address should not change until enabled')
# Enable the input
dut.i_enable_in = 1
yield from wait()
assert_o_address('0100', 'Address should change to 0100')
# Reset the address
dut.i_reset = 1
yield from wait()
assert_o_address('0000', 'Address should reset to 0000')
dut.i_reset = 0
yield from wait()
def program_counter(dut):
def assert_o_count(value, error_msg):
"""Check the value of the output count"""
assertions.assertEqual(dut.o_count.value.binstr, value, error_msg)
# Test initialization
yield from wait()
assert_o_count('xxxx', 'o_count should start disconnected')
# Pulse the clock, nothing should change:
yield from clock(dut)
assert_o_count('xxxx', 'o_count should still be disconnected')
# Enable the output:
dut.i_enable_out = 1
yield from wait()
assert_o_count('0000', 'o_count should be enabled and initialized')
# Increment:
dut.i_increment = 1
yield from wait()
assert_o_count('0000', 'o_count should not increment until clock pulse')
yield from clock(dut)
assert_o_count('0001', 'o_count should increment')
yield from clock(dut)
assert_o_count('0010', 'o_count should increment')
yield from clock(dut)
assert_o_count('0011', 'o_count should increment')
# Cycle without increment:
dut.i_increment = 0
yield from clock(dut)
assert_o_count('0011', 'o_count should not increment')
# Disable and Re-enable output:
dut.i_enable_out = 0
yield from wait()
assert_o_count('zzzz', 'o_count should disconnect')
dut.i_enable_out = 1
yield from wait()
assert_o_count('0011', 'o_count should re-enable')
# Reset:
yield from reset(dut)
assert_o_count('0000', 'o_count should reset')
# Test roll-over:
dut.i_increment = 1
# Increment over 8 cycles:
yield from clock(dut, 8)
assert_o_count('1000', 'o_count should be 8')
# Increment over 9 cycles, rolling over the count:
yield from clock(dut, 9)
assert_o_count('0001', 'o_count should roll-over back to 1')
def program_data(address, data):
dut.i_program_mode = 1
dut.i_address = address
dut.i_program_data = data
yield from cycle(dut, 1, ['i_write_enable'])
dut.i_program_mode = 0
yield from wait()
def mux_2x4(dut):
def assert_o_address(value, error_msg):
"""Check the value of the output address"""
assertions.assertEqual(dut.o_address.value.binstr, value, error_msg)
dut.i_address_1 = 0b0101
dut.i_address_2 = 0b1010
dut.i_input_select = 0
yield from wait()
assert_o_address('0101', 'Output address should be first input')
dut.i_input_select = 1
yield from wait()
assert_o_address('1010', 'Output address should be second input')
def reset_input():
dut.i_debug = True
dut.i_bus.value.binstr = 'zzzzzzzz'
dut.i_load_instruction = 0
dut.i_send_address = 0
dut.i_reset = 0
yield from wait()
def reset():
dut.i_opcode = 0b0000
dut.i_flag_carry = 0
dut.i_flag_zero = 0
dut.i_reset = 1
yield from wait()
dut.i_reset = 0
assert_step(0)
def register(dut):
def assert_o_bus(value, error_msg='wrong data'):
"""Check the bus out value"""
assertions.assertEqual(dut.o_bus.value.binstr, value, error_msg)
def assert_o_unbuffered(value, error_msg='wrong data'):
"""Check the unbuffered output"""
assertions.assertEqual(dut.o_unbuffered.value.binstr, value, error_msg)
def reset_input():
dut.i_bus = 0
dut.i_load_data = 0
dut.i_send_data = 0
dut.i_reset = 0
yield from wait()
#### Test initialization
yield from reset_input()
assert_o_bus('zzzzzzzz')
#### Test loading data
# Simulate an data on the bus:
dut.i_bus = 0b01000010
# Tell the register to load it:
dut.i_load_data = 1
yield from wait()
assert_o_unbuffered('01000010',
'Data should go to unbuffered out immediately')
yield from reset_input()
assert_o_bus('zzzzzzzz', 'Data should be latched in, but not output yet.')
#### Test sending data
dut.i_send_data = 1
yield from wait()
assert_o_bus('01000010', 'Data should be output now')
assert_o_unbuffered('01000010', 'Data should go to unbuffered still')
#### Test reset
yield from reset_input()
dut.i_reset = 1
yield from wait()
assert_o_bus('zzzzzzzz', 'bus output disconnected')
assert_o_unbuffered('zzzzzzzz', 'unbuffered data is now undefined')
def reset_input():
dut.i_debug = 1
dut.i_program_mode = 0
dut.i_program_data.value.binstr = 'zzzzzzzz'
dut.i_address.value.binstr = 'zzzz'
dut.i_write_enable = 0
dut.i_read_enable = 0
dut.io_data.value.binstr = 'zzzzzzzz'
yield from wait()
def assert_load_instruction(instruction):
opcode, operand = (instruction[:4], instruction[4:])
yield from reset_input()
dut.i_bus = int(instruction, 2)
yield from wait()
yield from cycle(dut, 1, ['i_load_instruction'])
assert_o_opcode(opcode,'opcode should be loaded immediately')
assert_o_address('zzzz','address bus should be silent until i_send_address=1')
dut.i_send_address = 1
yield from wait()
assert_o_opcode(opcode,'opcode should still be available')
assert_o_address(operand,'address should write to the bus')
yield from reset_input()
assert_o_opcode(opcode,'opcode should remember even when reset')
assert_o_address('zzzz','address bus is silent on reset')
dut.i_send_address = 1
yield from wait()
assert_o_opcode(opcode,'opcode should still be available')
assert_o_address(operand,'address should write to the bus again')
def pc_and_mar(dut):
def assert_o_address(value, error_msg):
"""Check the value of the output address"""
assertions.assertEqual(dut.o_address.value.binstr, value, error_msg)
yield from wait()
dut.i_enable = 1
yield from cycle(dut, 4, ('i_clock', 'i_increment'))
# MAR is one cycle behind PC, so after 4 cycles, MAR should contain 3
assert_o_address('0011', 'When PC has counted to 4, MAR should contain 3.')
yield from reset(dut)
assert_o_address('0000', 'MAR should reset to 0000.')
def reset_input():
dut.i_program_mode = 0
dut.i_program_address = 0b0000
dut.i_program_data = 0b00000000
dut.i_program_write = 0
# Each component has a seperate debug line to selectively enable:
dut.i_debug_pc = True
dut.i_debug_mar = True
dut.i_debug_ir = True
dut.i_debug_ram = True
dut.i_debug_bus = True
dut.i_debug_control = True
dut.i_debug_out = True
dut.i_debug_register_A = True
dut.i_debug_register_B = True
yield from wait()
def reset():
yield from reset_input()
dut.i_reset = 1
yield from wait()
dut.i_reset = 0
yield from wait()
def reset_input():
dut.i_bus = 0
dut.i_load_data = 0
dut.i_send_data = 0
dut.i_reset = 0
yield from wait()
def alu_test(dut):
def assert_o_bus(value, error_msg='wrong data'):
"""Check the bus out value"""
assertions.assertEqual(dut.o_bus.value.binstr, value, error_msg)
def assert_overflow(overflow=True, error_msg='expected overflow flag did not register'):
"""Ensure that the overflow flag was set (or not)"""
assertions.assertEqual(dut.o_flag_overflow.value.binstr, '1' if overflow else '0', error_msg)
def assert_zero(zero=True, error_msg='expected zero flag did not register'):
"""Ensure that the zero flag was set (or not)"""
assertions.assertEqual(dut.o_flag_zero.value.binstr, '1' if zero else '0', error_msg)
def reset_input():
dut.i_a = 0
dut.i_b = 0
dut.i_subtract = 0
dut.i_send_result = 0
yield from wait()
### Test init
yield from reset_input()
assert_o_bus('zzzzzzzz', 'Output should default disabled')
### Test add
dut.i_a = 22
dut.i_b = 42
dut.i_send_result = 1
yield from wait()
assert_o_bus('01000000', '22 + 42 = 64')
assert_overflow(False)
assert_zero(False)
### Test subtract
yield from reset_input()
dut.i_a = 34
dut.i_b = 30
dut.i_subtract = 1
dut.i_send_result = 1
yield from wait()
assert_o_bus('00000100', '34 - 30 = 4')
assert_overflow(False)
assert_zero(False)
### Test negative numbers
yield from reset_input()
dut.i_a = 29
dut.i_b = 56
dut.i_subtract = 1
dut.i_send_result = 1
yield from wait()
assert_o_bus('11100101', '29 - 56 = -27')
assert_overflow(False)
assert_zero(False)
### Test numbers larger than we handle:
yield from reset_input()
dut.i_a = 127
dut.i_b = 127
dut.i_send_result = 1
yield from wait()
assert_o_bus('11111110', '127 + 127 = -2 with overflow')
assert_overflow()
assert_zero(False)
### Test zero flag:
yield from reset_input()
dut.i_a = -2
dut.i_b = 2
dut.i_send_result = 1
yield from wait()
assert_o_bus('00000000','-2 + 2 = 0')
assert_zero()
### Test disconnection from bus
dut.i_send_result = 0
yield from wait()
assert_o_bus('zzzzzzzz', 'Should disconnect from bus')
def reset_input():
dut.i_a = 0
dut.i_b = 0
dut.i_subtract = 0
dut.i_send_result = 0
yield from wait()
def ram_16x8(dut):
def assert_io_data(value, error_msg):
"""Check the value of the data lines"""
if (isinstance(value, numbers.Number)):
assertions.assertEqual(dut.io_data.value, value, error_msg)
else:
assertions.assertEqual(dut.io_data.value.binstr, value, error_msg)
def reset_input():
dut.i_debug = 1
dut.i_program_mode = 0
dut.i_program_data.value.binstr = 'zzzzzzzz'
dut.i_address.value.binstr = 'zzzz'
dut.i_write_enable = 0
dut.i_read_enable = 0
dut.io_data.value.binstr = 'zzzzzzzz'
yield from wait()
def assert_read(address, value, error_msg='wrong data read'):
dut.i_address = address
dut.i_read_enable = 1
yield from wait()
assert_io_data(value, error_msg)
dut.i_read_enable = 0
yield from wait()
def write_data(address, data):
dut.i_address = address
dut.io_data = data
yield from cycle(dut, 1, ['i_write_enable'])
def program_data(address, data):
dut.i_program_mode = 1
dut.i_address = address
dut.i_program_data = data
yield from cycle(dut, 1, ['i_write_enable'])
dut.i_program_mode = 0
yield from wait()
def assert_write(address, data, error_msg='Could not verify written data'):
yield from write_data(address, data)
yield from assert_read(address, data, error_msg)
# Initialize
yield from reset_input()
yield from wait()
assert_io_data('zzzzzzzz', 'No output should be made on initialization')
# Verify all RAM is cleared
yield from reset_input()
for addr in range(16):
assert_read(addr, '00000000', 'RAM address is cleared')
# Manually enter new RAM data
yield from reset_input()
data = [random.randint(0, 255) for x in range(16)]
for addr in range(16):
yield from program_data(addr, data[addr])
assert_io_data('zzzzzzzz',
'No output should be available unless read is enabled')
# Read from RAM
yield from reset_input()
for addr in range(16):
assert_read(addr, data[addr])
# Write data from the io_data bus
yield from reset_input()
yield from assert_write(0b0010, 0b11001100)