|Short desc.||Series of specific ports that read keyboard key presses.|
|Bit Mask||%xxxx xxxx ---- ---0 where only one bit in x is 0|
Reads keys on the keyboard depending on the upper byte of the port number. The five keys are represented by bits 0-4 of the read byte, listed below with bit 4 first down to bit 0. A zero means that the key is pressed.
The top eight bits of the port address are active low signals that select one or more key rows for reading.
|Port upper byte||Keys affected (row of keys)|
|$7F (bit 7)||B, N, M, Symbol Shift, Space|
|$BF (bit 6)||H, J, K, L, Enter|
|$DF (bit 5)||Y, U, I, O P|
|$EF (bit 4)||6, 7, 8, 9, 0|
|$F7 (bit 3)||5, 4, 3, 2, 1|
|$FB (bit 2)||T, R, E, W, Q|
|$FD (bit 1)||G, F, D, S, A|
|$FE (bit 0)||V, C, X, Z, Caps Shift|