inhibit();
}
+/*
+Host to Keyboard
+----------------
+Data bits are LSB first and Parity is odd. Clock has around 60us high and 30us low part.
+
+ ____ __ __ __ __ __ __ __ __ __ ________
+Clock \______/ \_/ \_/ \_/ \_/ \_/ \_/ \_/ \_/ \_/
+ ^ ____ ____ ____ ____ ____ ____ ____ ____ ____ ____ ___
+Data ____|__/ X____X____X____X____X____X____X____X____X____X \___
+ | Start 0 1 2 3 4 5 6 7 P Stop
+ Request by host
+
+Start bit: can be long as 300-350us.
+Request: Host pulls Clock line down to request to send a command.
+Timing: After Request keyboard pull up Data and down Clock line to low for start bit.
+ After request host release Clock line once Data line becomes hi.
+ Host writes a bit while Clock is hi and Keyboard reads while low.
+Stop bit: Host releases or pulls up Data line to hi after 9th clock and waits for keyboard pull down the line to lo.
+*/
uint8_t ibm4704_send(uint8_t data)
{
bool parity = true; // odd parity
}
/*
-Keyboard to Host:
-Clock ~~~~___~~_~~_~~_~~_~~_~~_~~_~~_~~_~~~~~~~~ H:60us/L:30us
-
-Data ____~~X==X==X==X==X==X==X==X==X==X________
- | 0 1 2 3 4 5 6 7 P(odd)
- | LSB MSB
- Start bit(80us)
+Keyboard to Host
+----------------
+Data bits are LSB first and Parity is odd. Clock has around 60us high and 30us low part.
+
+ ____ __ __ __ __ __ __ __ __ __ ________
+Clock \____/ \_/ \_/ \_/ \_/ \_/ \_/ \_/ \_/ \_/
+ ____ ____ ____ ____ ____ ____ ____ ____ ____ ____
+Data ____/ X____X____X____X____X____X____X____X____X____X________
+ Start 0 1 2 3 4 5 6 7 P Stop
+
+Start bit: can be long as 300-350us.
+Inhibit: Pull Data line down to inhibit keyboard to send.
+Timing: Host reads bit while Clock is hi.
+Stop bit: Keyboard pulls down Data line to lo after 9th clock.
*/
uint8_t ibm4704_recv(void)
{