1.6.2. Memory Back-up Circuit
The battery [A] on the MBU backs up the RAM on the MBU, which contains
system parameters. It also backs up the real time clock in the cpu. This bat-
tery is not rechargeable. CN1-9 tells the cpu whether the back-up power
(CN1-11) comes from the battery or from the + 5V supply.
A rechargeable battery [B] backs up the SAF memory and the real time clock
for 1 hour. When the main power is switched on, the + 24V supply charges
the battery. If there is data in the SAF, the battery also backs up the real time
clock, to preserve the MBU battery.
Battery
+5V
Regulator
SAF
Memory
+24V
Battery
Switch
Battery
+5V
Voltage
Detector
Switching
Circuit
RAM
CPU
Memory
Monitor
1-11
1-11
1-9
1-9
MBU
FCU
Real Time
Clock
5-1
Switching
Circuit
5-2
[A]
[B]
Reference:
Group 3
Facsimile
Manual,
section 1-4-3
(Circuit type 1)
November 30th, 1991
OVERALL MACHINE INFORMATION
POWER DISTRIBUTION
1-12
Summary of Contents for FAX500
Page 1: ...FAX550 SERVICE MANUAL...
