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8. Low battery circuit
q
Vin
ie:
Ro4
GND
1
+5VOC
BATT FAULT
ASIC
9. Tablet circuit
Voltage Vin inputted from the battery or the AC adapter is inputted to
1C23 voltage detection input pin (2 pin). IC23 is monitoring.
When in low battery, if this voltage falls below 3V, IC23_ judges it as.
BATT FAULT signal and tums 1 pin active.
BATT FAULT signal is inputted to ASIC. When ASIC detects this
signal, it terminates the current operation forcibly and tums off the
power.
The voltage falls to BATT FAULT voltage by battery exhaustion.
When the battery is replaced with new one and the power voltage
recovers,
the operation is started by turning
on the power ON SW.
Low battery detection by the hardware is only BATT FAULT. Low
battery display during the OS operation is performed by judging the
battery voltage detected from the AD convertor with the software.
The SV convertor output is monitored by IC21. When +5V DC output
falls below 4.5V, the above BATT FAULT operation is performed.
This is to protect the memory in case of abnormality such as break-
down of the SV convertor.
as
1
a
lta
[i
}
INT
VRPPP ON
AD CONVST }-———_____
YMON
if
* Tablet circuit description
* OS mode
The tablet control TR, the AD convertor, and the ASIC are used to
detect the transparent tablet position.
The A/D convertor converts 227?
converts the analog voltage into 12-bit data
tablet positions, 277? pressed ??? X, Y direction 277
(if the pressed level is judged as equal to or higher than the
specified level, conversion is performed.)
The tablet applies a voltage in X and Y directions in time division
with the control TR. In the X direction measurement,
a voltage
corresponding to the pressed position is outputted to YL In the Y
direction measurement, it is outputted to XL.
The ASIC controls the A/D convertor and the control TR.
To reduce power consumption in the OS mode, the tablet input
interruption is detected with INIT signal by the ASIC. Only when
there is a tablet input, the AD7880 is switched from the power
save mode to the normal mode by the control of ASIC and the
AD7880 is operated. (For switching from the power save mode to
the normal mode, the AD7880 mode pin is used. When MODE =
L, the power save mode. When MODE = H, the norma! mode.)
* Diag mode
During a diag operation, INIT signal interruption is not used and
the AD7880 always detects inputs of the X axis and the Y axis of
the tablet.
Therefore, the tablet input operation differs between the OS
operations and the diag operations. If the tablet operates normally
only in the diag mode and does not operate normally in the OS
mode, check MON, XMON, and YMON pins.
10. PCMIA card interface
The major function of the PCMIA card is to send and receive data
between the card and the CPU or the system memory. Though
ARM610 data bus is of 32 bits, the PCMIA data bus is of 16 bits. So
16-bit data are converted into 32-bit inside the ASIC and an access is
made.
The PCMIA supports two types; the memory card type and the VO
card type.
For the corresponding memory card, PCMAIA 2.0 version mask
ROM, EPROM, flash memory, and SRAM card can be used. (some
cards may require installation of a special card driver.) the VO card
allows the use of a Modem and LAN.
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