ps2_host

Files
file	ps2_host.cdl
	PS2 interface for keyboard or mouse.

Detailed Description

Modules

module ps2_host::ps2_host	(	clock	clk,
		input bit	reset_n,
		input t_ps2_pins	ps2_in,
		output t_ps2_pins	ps2_out,
		output t_ps2_rx_data	ps2_rx_data,
		input bit	divider[16]
	)

As a PS2 host, to receive data from the slave (the first target for the design), the module:

1. Looks for clock falling
2. If data is low, then assume this is a start bit. Set timeout timer.
3. Wait for clock falling. Clock in data bit 0
4. Wait for clock falling. Clock in data bit 1
5. Wait for clock falling. Clock in data bit 2
6. Wait for clock falling. Clock in data bit 3
7. Wait for clock falling. Clock in data bit 4
8. Wait for clock falling. Clock in data bit 5
9. Wait for clock falling. Clock in data bit 6
10. Wait for clock falling. Clock in data bit 7
11. Wait for clock falling. Clock in parity bit.
12. Wait for clock falling. Clock in stop bit.
13. Wait for clock high.
14. Validate data (stop bit 1, parity correct)

If a timeout timer expires, which could happen if the framing is bad, then an abort can be taken.

Parameters

[in]	clk	Clock
[in]	reset_n	Active low reset
[in]	ps2_in	Pin values from the outside
[out]	ps2_out	Pin values to drive - 1 means float high, 0 means pull low
[out]	ps2_rx_data	PS2 receive data from the device, in parallel
[in]	divider	Clock divider input to generate approx 3us from clk