Epson PX-8 Technical Manual page 83

REV.-A
2.5.1.3 J3
J3 is a maintenance purpose jumper used for testing the sub-
CPU 7508. To open (set off) this jumper, put the jumper block
as shown in Fig. 2-62; leaving one terminal pin open. OFF is
the standard setting. The ON setting disables the normal sub-
CPU operation.
2.5.1.4 J4
~~------------~~
Fig. 2-62
Jumper J4 allows for pull-up of the analog input (ANIN) signal input. Because the ANIN signal
input voltage ranges from 0 to +2.0V, the jumper may need to be reset depending on the connect-
ed analog device.
2.5.1.5 J5
Jumper J5 is used to eliminate vertical ghost display lines which may appear due to the charac-
teristics of the LCD unit. Its setting depends on the installed LCD unit (or the LCD panel, to be
precise). J5 may need to be reset when the LCD unit is replaced so that ghosts, if observed,
are eliminated.
2.5.2
Switches
Five switches are mounted on the MAPLE board as shown in Fig. 2-61. Their functions are de-
tailed in the following.
2.5.2.1 SW1
This switch is used to turn the computer on and off. It is connected to a port of the sub-CPU
7508 which controls power on/off by sensing a setting change of this switch. Thus, it may be in-
effective when the sub-CPU loeses the normal power-on/off sequence control capability because
the computer can, through a programming error, got into a software loop.
2.5.2.2 SW2
This is the RESET switch which is accessible at the left side of the computer. It is connected to
another port of the sub-CPU. The switch causes all of the computer sections except for the sub-
CPU to be initialized, it is ineffective when the sub-CPU is not operating normally.
2.5.2.3 SW3
This switch allows the user to enable or disable the charging and discharging circuits for the auxi-
liary battery, soldered on the MAPLE board. It is provided in order to prevent complete auxiliary
battery discharge and thereby protect the battery from deterioration when the PX-8 unit is stored
unused for a long period of time. The switch must be set ON whenever the board is in service,
otherwise, the normal backup operation would not be in effect. After a low voltage condition is
detected, the Ni-Cd battery life is shortened if left completely discharged.
2-59