i2c_bus_monitor

Monitor SCL and SDA for START/STOP, bus-free, and active/inactive timeouts.

The monitor runs while controller, multi-controller or target mode is enabled. A START or STOP is reported once SCL has stayed high for thd_dat_i cycles after the SDA edge. thd_dat_i is the data hold time (< 200 ns, < thd_sta). t_buf_i is the bus free time (< 5 us). bus_active_timeout_i covers SCL held low (~25 ms); bus_inactive_timeout_i covers SCL held high with SDA stable (~50 us), and zero disables it.

Ports

Table 1. Ports
Name	Direction	Type	Description
`clk_i`	input	`logic`	System clock.
`rst_ni`	input	`logic`	Async reset, active-low.
`scl_i`	input	`logic`	SCL pad input.
`sda_i`	input	`logic`	SDA pad input.
`controller_enable_i`	input	`logic`	Controller mode enabled.
`multi_controller_enable_i`	input	`logic`	Multi-controller mode enabled; the bus starts busy and bus_free_o is high only in the free state.
`target_enable_i`	input	`logic`	Target mode enabled.
`target_idle_i`	input	`logic`	Target FSM is idle; suppresses event_host_timeout_o.
`thd_dat_i`	input	`logic [12:0]`	Data hold time in clocks (< 200 ns, < thd_sta); also the START and STOP qualification delay.
`t_buf_i`	input	`logic [12:0]`	Bus free time in clocks (< 5 us), counted after a STOP.
`bus_active_timeout_i`	input	`logic [29:0]`	SCL-low timeout threshold in clocks (~25 ms).
`bus_active_timeout_en_i`	input	`logic`	Enable SCL-low timeout.
`bus_inactive_timeout_i`	input	`logic [30:0]`	SCL-high timeout threshold in clocks (~50 us); zero disables it.
`bus_free_o`	output	`logic`	Bus free for a new transfer; outside multi-controller mode low only during the t_buf_i wait after a STOP.
`start_detect_o`	output	`logic`	One-cycle pulse on a qualified START or repeated START.
`stop_detect_o`	output	`logic`	One-cycle pulse on a qualified STOP.
`event_bus_active_timeout_o`	output	`logic`	One-cycle pulse when SCL is held low past the threshold while bus_active_timeout_en_i is set.
`event_host_timeout_o`	output	`logic`	Pulse when SCL is held high past the threshold while the target is not idle.