Serial loop-back test – HP 48g Graphing Calculator User Manual
Page 450
Attention! The text in this document has been recognized automatically. To view the original document, you can use the "Original mode".
B will appear at the top left corner of the display. If OK appears
to the right of IRLB, the calculator passes this test. If OK doesn’t
appear, the calculator requires service.
1. Press and hold
2. Press and release the “C” key (the key with C next to it).
3. Release
(ON
). The empty stack display should appear.
Serial Loop-Back Test
This test checks the operation of the send and receive circuits of the
serial interface at the top of the calculator.
1. Turn on the calculator.
2. Press and hold
(ON ).
3. Press and release the “D” key (the key with D next to it).
4. Release
(ON
). A vertical line will appear at both sides and at the
center of the display.
5. Temporarily connect (short) the middle two pins (pins 2 and 3)
of the 4-pin serial connector at the top end of the calculator. Be
careful not to bend or severely jar the pins. You must have this
connection bridged during the entire duration of the test.
6. Press (PR^.
U_LB will appear at the top left corner of the display. If OK appears
to the right of U_LB, the calculator passes this test. If OK doesn’t
appear, the calculator requires service.
Note
If you inadvertently short pins 1 and 2 or pins 3
and 4 of the serial connector, the loop-back test will
return U_LB 00001 or U_LB 80002 (test-failed
message), but you will not damage the calculator.
A-14 Support, Batteries, and Service