Epson PX-8 - Page 36

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REV.-A
• When eight hours have elapsed after the ac adaptor is connected to the AC line, port 41 of the
4-bit sub-CPU goes high, cutting off transistor 09. This puts the circuit in the trickle charging
state by inserting the resistors R3 and R5 (combined resistance, 41 ohms) in the charging path
in series. The circuit constants are selected in this state so that the battery is substantially not
harmed by overcharge, even if the battery is continually charged.
*Reference
Following is the sub-CPU port operation for power control:
Table 2-2 Sub-CPU Port Operation
Port
Direction Meaning
Signal
Function
level
Power switch
Low Power switch "OFF" interruption (H -+ L: ~)
POO IN
interruption High Power switch "ON" interruption (L -+ H: -.r )
Main battery Low Inactive
P23 Out
voltage detection High Active. Supply main battery voltage to AID
converter
• Supply operational voltage to AID
converter
Low Reset main CPU, slave CPU, etc.
P40 out Reset
High Inactive
Recharging
mode
Low
Normal recharging mode
P41
Out
control High Trikle recharging mode
P42 Out
Battery back-up Low
Back-up with main battery
control High Back-up with auxiliary battery
Low
Active source input of "P40" and "OFF"
P60 In Reset switch
High Inactive
AC adapter (re-
Low No AC adapter (non recharging condition)
P61 In
charging opera-
tion)
detect
High Recharging condition (AC adapter is plugged)
Recharging
mode Low
Normal recharging mode
P63 Out
for auxiliary bat-
High Trikle recharging mode
tery
Low Power ON
P70 Out
Powr ON
High Power OFF
"OFF" signal for
Low
Active (Initialize the '4C' '6A')
P71
Out
gate array (6A, 4C) High Inactive
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