IOP16 PS/2 Keyboard

PS/2 Keyboard

• Wrapper for PS/2 keyboard interfaces
• PS/2 to ASCII conversion

Software Interface

Status register (Read only)

• Addr = 0
• Value = 0x00, No data present
• Value = 0x01, Data present

Data register (Read only)

• Addr = 1
• ASCII Data

PS/2 Keyboard Subroutines

Get character from keyboard

• Blocking routine waits for keypress
• Returns ASCII key value in Reg1

RDKBD	JSR	WTKBRX		WAIT FOR KBD RX CHAR
	IOR	0X01	0X0D	READ KBD CHAR
	RTS			
WTKBRX	IOR	0X01	0X0C	READ KBD STATUS
	ARI	0X01	0X01	RX RDY BIT
	BEZ	WTKBRX		LOOP UNTIL CHAR PRESENT

Poll the keyboard

• Returns keyboard status in Reg1
  • Returns 0x00 = No key
  • Returns 0x01 - Key was pressed

POLLKBD	IOR	0X01	0X0C
	RTS		

Hook-up

• Add to Top Level VHDL code

Pins

• Add to top level entity pins list

  -- PS/2 
  ps2Clk  : inout std_logic;
  ps2Data : inout std_logic;

Signals

• Add signal into architecture section

-- Decodes/Strobes
...
 signal w_kbcs : std_logic;

-- Interfaces
...
  signal w_KbdData  :  std_logic_vector(7 downto 0);

VHDL Instance

-- PS/2 keyboard/mapper to ANSI
KEYBOARD : ENTITY  WORK.Wrap_Keyboard
port MAP (
  i_CLOCK_50 => i_clk,
  i_n_reset  => w_resetClean_n,
  i_kbCS     => w_kbcs,
  i_RegSel   => w_periphAdr(0),
  i_rd_Kbd   => w_kbcs,
  i_ps2_clk  => ps2Clk,
  i_ps2_data => ps2Data,
  o_kbdDat   => w_KbdData
);

Hook-up Strobes/Read Mux

• Add to strobes and read mux

-- Strobes/Selects
  ...
  w_kbcs <= '1' when (w_periphAdr(7 downto 1) = "0000110") and (w_periphRd = '1') else '0';

-- Peripheral bus read mux
  w_periphIn <= ...
    w_KbdData  when w_periphAdr(7 downto 1) = "0000110"	else
  ...

Resources

• Logic Cells: 708
• Registers: 95
• Memory Bits: 0
• M9Ks: 0