Key Matrix and Key-Input Data Storage RAM
The key matrix is of 12 4 configuration, as shown below.
The data of each key is stored as illustrated below, and is read by a read command, starting from the least
b0------------ b3 b4 ------------b7
When the most significant bit of data (Seg12 b7) has been read, the least significant bit of the next data (Seg1 b0) is
Data is written to the LED port by a write command, starting from the least significant bit of the port. When a bit of
this port is 0, the corresponding LED lights; when the bit is 1, the LED goes off. The data of bits 6 through 8 is
− − − b4 b3 b2 b1 b0
On power application, all the LEDs remain dark.