axi_lite_mailbox_unit

Expose NUM_MAILBOXES AXI-Lite mailboxes with inbound and outbound IRQs.

Independent mailboxes share one AXI-Lite slave decode sized by MAILBOX_BASE_ADDR and MAILBOX_SIZE. Each mailbox is an axi_lite_mailbox with two AXI-Lite ports of MAILBOX_SIZE bytes each: mailbox m places its outbound port at MAILBOX_BASE_ADDR + 2 * m * MAILBOX_SIZE and its inbound port one MAILBOX_SIZE above it. The axi_lite_demux decodes only the base-relative address bits from $clog2(MAILBOX_SIZE) upward that select a port. Each mailbox has depth MAILBOX_DEPTH and raises inbound_interrupt_o and outbound_interrupt_o as level-sensitive, active-high interrupts.

Parameters

Table 1. Parameters
Name	Type	Default	Description
`NUM_MAILBOXES`	`int unsigned`	`2`	Number of mailboxes, each with an outbound and an inbound port.
`MAILBOX_DEPTH`	`int unsigned`	`8`	FIFO depth per mailbox. In entries, for each internal message FIFO.
`MAX_TRANS`	`int unsigned`	`32`	AXI-Lite outstanding capacity. Maximum open AXI-Lite transactions per channel in the port demux.
`MAILBOX_BASE_ADDR`	`int unsigned`	`32'h0`	Byte base of mailbox 0. The aperture decode is relative to it.
`MAILBOX_SIZE`	`bit [31:0]`	`32'h800`	Byte span per mailbox port. Register space of one port of an axi_lite_mailbox; a mailbox spans twice this. Must be a power of two.
`ADDR_WIDTH`	`int unsigned`	`32`	AXI-Lite address width.
`DATA_WIDTH`	`int unsigned`	`64`	AXI-Lite data width.
`StrbWidth`	`int unsigned`	`DATA_WIDTH / 8`	Write-strobe width.
`MailboxSizeW`	`int unsigned`	`$clog2(MAILBOX_SIZE)`	Lowest address bit of the port select.

Ports

Table 2. Ports
Name	Direction	Type	Description
`clk_i`	input	`logic`	System clock. Clocks all mailbox logic and the AXI-Lite interface; the unit has one clock domain.
`rst_ni`	input	`logic`	Async reset, active-low. Initializes all mailbox state.
`test_en_i`	input	`logic`	DFT test enable, driven to the demux and mailbox test inputs.
`mailbox_axi_req_i`	input	`axi_req_t`	AXI-Lite slave request.
`mailbox_axi_resp_o`	output	`axi_resp_t`	AXI-Lite slave response.
`inbound_interrupt_o`	output	`logic [NUM_MAILBOXES-1:0]`	Per-mailbox interrupt of the inbound port.
`outbound_interrupt_o`	output	`logic [NUM_MAILBOXES-1:0]`	Per-mailbox interrupt of the outbound port.