Epson 20 - Manual (Page 152)

For this check, the program writes specific data into memory and
then reads it back. The data is written and read in blocks of 64KB. A
parity check is also made on each block. A memory count displays
after each block tests without error. After the program checks the last
block, you see a message such as the following:
000640 KB OK
If an error occurs, make a copy or a printout of the error code and
message, and contact your Epson dealer or service center. Attempting
to correct memory errors yourself may violate your warranty
agreement.
Keyboard Check
Use this option to check the operation and the configuration of the
keyboard. The program first checks the keyboard controller; during
this check, you see the green indicator lights on the keyboard flash.
Before checking the operation of the keys, you must identify your
keyboard layout so the test is appropriate for the keys on your
keyboard. A display appears, asking you to identify the shape of your
Enter key. Choose the shape that matches your system, then press
Enter. You can exit the keyboard test by pressing 0 and Enter.
The program displays your keyboard layout on the screen. When you
press a key on the keyboard, an asterisk appears at the corresponding
location on the keyboard layout. If you hold a key down, the asterisk
begins to blink. If an asterisk does not appear at the correct location,
there is a problem with your keyboard. Test each key.
C-8 Performing System Diagnostics