5. PROCEDURES BEFORE SYSTEM OPERATION
MELSEC-A
5-6
5.4
Execution Method for Self-diagnosis
This section covers the procedure for entering the self-diagnosis mode and the LED displays
descriptions.
A self-diagnosis is automatically performed by setting the rotary switch to 2 and starting up (using the
power supply on or reset switch).
During an internal diagnosis the LED display corresponds to the B0 to B6 statuses and the test
responses being conducted are shown below.
Meaning
B6
B5
B4
B3
B2
B1
B0
TEST
(a) MPU test
During test
{
{
{
{
{
z
z
z
Error
z
{
{
{
{
z
{
z
(b) Timer test
During test
{
{
{
{
z
{
z
z
Error
z
{
{
{
z
{
{
z
(c) Interrupt test
During test
{
{
{
{
z
z
z
z
Error
z
{
{
{
z
z
{
z
(d) DRAM test
{
{
{
z
{
z
z
z
{
{
{
z
z
{
z
z
Error
z
{
{
z
z
z
{
z
{
: Turned off
z
: Turned on
When the test results are normal, tests (a) to (d) are repeated. If an error is detected, then the
LED status at the tie the error occurs for that test will be displayed.
During test