Battery Installation - Canon EOS 55 Service Manual

Part 2: Technical Information
2.4 Battery Installation
1) MPU Initial Sequence
1. When the battery is installed, VBAT is applied to the DC/DC Convertor, which
generates VDD (4.7V) and applies it to the LCD-DR and MPU. Also, when the bat-
tery is installed, it opens the RESET switch applying the 32. 768KHz clock to the
LCD-DR.
2. Simultaneously, the /El ON pin of the LCD-DR goes low, turning on the DC/DC.
3. When the DC/DC's El exceeds 4.5V, the EF-IC's /RES2 goes high. When the
LCD-DR see this change on /RESIO, the LCD-DR switches /RESMPU to high.
4. This resets the MPU and the 16MHz clock is generated.
5. Approximately 8ms after the 16MHz clock starts, the MPU is operational.
2) Switch Input Sequence
1.
When it senses a switch change, LCD-DR sends /LCDREQ low.
2. Simultaneously, the /El ON pin of the LCD-DR goes low, turning on the DC/DC.
3. When the DC/DC's El exceeds 4.5V. the EF-IC's /RES2 goes high. When the
LCD-DR see this change on /RESIO, the LCD-DR switches /RESMPU to high.
4. This resets the MPU and the 16MHz clock is generated.
5. Approximately 2ms after the 16MHz clock starts. the MPU is operational.
3) Low Battery Sequence
VBAT
P.GND
1.
EFIC always monitors El. During operation or at start-up ofDC/Dc, if El is
below 4.2V, EFIC not only resets, but also sends /RES2 low.
2. When the LCD-DR see this change on /RESIO, it switches /ElON to high and
/RESMPU to low. This turns the DC/DC and it remains off until another switch
input is received.
3. When the MPU sees /RESMPU go low, it senses operations and goes into stand-
by mode.
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Fig. 2-25 Battery Installation
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