HP 330 Service Information Manual page 142

50
or
60 Hz CRT
Ac line voltage is either 50 Hz or 60 Hz. A monitor's vertical sweep frequency may cause display
flicker if an incompatibility exists between the ac line frequency and the vertical sweep frequency.
These options permits the user to set the video board for the local line voltage frequency.
The 50/60 Hertz CRT options are only available with non-bit-mapped video cards. With one
of these cards installed, if
m
or []] is pressed, a soft override of the power-up CRT frequency
occurs. The power-up CRT frequency of the HP 98546 Display Compatibility Interface is
determined by a switch on its video card. When this switch is set to 0, the power-up default
is 60 Hz, when this switch is set to 1, the power-up default is 50 Hz. If
m
or
rn
is pressed
during configure mode when there is both an alpha/graphics video card set and a bit mapped
video board present, then the key pressed will effect the alpha display (even though the '5' and
'6' are not displayed). If no alpha/graphics video card set is present and
m
or []] is pressed,
the Boot ROM will re-enter self test, but the display will not be effected.
An example Configure Mode display with 50/60 Hz information is shown in Figure 4-2.
Copyright 1985,
Hewlett-Packard Company.
All Rights Reserved.
BOOTROM Rev. A2
Bit Mapped Display
Console Keyboard at XX
Graphics
HP-IB
DMA-CO
HP98644 at 2
HP98625 at 8
HP98629 at 20
8388608 Bytes
CONFIGURE MODE
RESET To Power-Up
KEY ACTION
T
L
6
5
Extended Self-Test
Continuous Self-Test Loop
60 Hz CRT
50 Hz CRT
Figure 4-2. Configure Mode Screen Display with 50/60 Hz Information
126
Boot ROM Functions
1H