memory¶

class memory.Register(name, nbytes=4, offset=0, mode='r', default_val=0, ram=False, ram_size=-1, data_width=32, axi4lite_mode='')[source]¶

__init__(name, nbytes=4, offset=0, mode='r', default_val=0, ram=False, ram_size=-1, data_width=32, axi4lite_mode='')[source]¶

A class to encapsulate a register’s parameters. This is used when instantiating a device with a large address space, but it is desirable to be able to address sub-spaces of this memory with separate names.

For example (see sys_block.py):

class sys_block(YellowBlock):
    def initialize(self):
        self.typecode = TYPECODE_SYSBLOCK
        self.add_source('sys_block')
        # the internal memory_map
        self.memory_map = [
            Register('sys_board_id',   mode='r',  offset=0),
            Register('sys_rev',        mode='r',  offset=0x4),
            Register('sys_rev_rcs',    mode='r',  offset=0xc),
            Register('sys_scratchpad', mode='rw', offset=0x10),
            Register('sys_clkcounter', mode='r',  offset=0x14),
        ]
    def modify_top(self,top):
        inst = top.get_instance('sys_block', 'sys_block_inst')
        inst.add_parameter('BOARD_ID', self.board_id)
        inst.add_parameter('REV_MAJ', self.rev_maj)
        inst.add_parameter('REV_MIN', self.rev_min)
        inst.add_parameter('REV_RCS', self.rev_rcs)
        inst.add_port('user_clk', 'user_clk')
        inst.add_wb_interface('sys_block', mode='r', nbytes=64, memory_map=self.memory_map, typecode=self.typecode)

Parameters:

name (String) – The name of this register
nbytes (Integer) – Number of bytes this register occupies
offset (Integer) – Location, in bytes, where this register resides in memory, relative to the base address of the device.
mode (String) – Read/write permission for this register. ‘r’ (readable), ‘w’ (writable), ‘rw’ (read/writable)
default_val (Integer or hex string) – Default value for register to be reset to and initialized. Eg (0xa, 10, or “a”)
ram (Boolean) – Whether the register is a RAM or not.
ram_size (Integer) – Size of the RAM
data_width (Integer) – Width of the data to be stored in this register.
axi4lite_mode (String) – Mode of the axi4lite interface. Eg. axi4lite_mode = ‘raw’, instantiates a raw axi4lite device.