Power On Reset - IBM 6360 Product Support Manual

When a switch-off occurs, the power
supply will turn on one of the top
three LEDs located on panel 1 to indi-
cate which type of switch-off occurred
(Figure 6-12).
LED A
LED B
LEDC
Indicates overvoltage
or undervoltage
Indicates
overcurrent
Indicates overheat
Figure 6-12. Electronics
(Rear View)
Panel
POWER ON RESET
1
A power on reset (POR) sequence occurs
each time the system power is turned
on. It ensures the electronic logic
is set to start at a specific point.
The power supply generates two reset
signals to start the POR sequence.
The first reset signal, POR system
signal (-PORSYS), is sent to the sys-
tem card. This signal permits the·
system card to generate a signal named
system power on reset (-SPOR). The
-SPOR signal initializes (resets) the
system logic.
The second power supply POR signal,
POR disconnect (-PORDIS), is sent to
the diskette adapter card and has two
functions. The first is to inhibit
the write gate and the erase gate to
prevent the writing on, or the erasing
of, a diskette during power on reset.
The second function is to initialize
(reset) the diskette adapter card.
Note: Very fast power ON/OFF cycles
are not recommended. This may prevent
correct POR signal voltage levels.
Whenever the power supply detects an
error and turns on LEDs A or B, the
power switch must be turned off for a
minimum of eight seconds. This will
allow the error detection circuits
enough time to reset.
6-14 IBM Displaywriter Product Support Manuat