Epson PX-8 - Page 82

REV.-A
Jumpers and Switches
Fig. 2-61 shows the locations of the jumpers and switches used on the MAPLE board and illus-
trates
their setting positions (ON/OFF, A/B, etc.).
OFF c!g1
ON ClQj
L-J4
,JtJ-----;
AC~
B ClQj
2.5.1 Jumpers
nOFF
~ON
SW2
r
SW4
ON ~i OFF
Fig.2-61 MAPLE Board Jumpers and Switches
The functions of the individual jumpers are detailed in the following (see Table 2-10 for a sum-
mary of their functions).
2.5.1.1 J1
This jumper is provided in order to permituse of either of two available main CPU types. (The main
CPU is located at 4A on the MAPLE board.) One of two terminals may be selected, T and N ter-
minals, respectively, disable and enable the HLTA signal line, reconciling the difference in Line
control between the two types of main CPUs. (The line relates to the DRAM refresh.)
T - Terminal T is selected
when a TOSHIBA CPU (parts No. X400084005) is used. When the T
and center
terminals are jumpered, the main CPU output signal, HLTA is disabled. (The ter-
minal is open; i.e., not connected to any other terminal.)
N - Terminal N is selected
when a NEC CPU (parts No. X400070008) is used.
* Caution: Examine the main CPU type before setting this jumper.
2.5.1.2 J2
This jumper is provided to allow for protection against main battery overcharge. When the ON
and center
terminals are jumpered, the control by the sub-CPU 7508 is disabled, forcing a normal
(high current) charge to be maintained as long as the ac adaptor is connected. This setting
may result in an overcharge condition of the main battery, which may shorten its life.
2-58