Furuno NX-700B Service Manual page 94

Memory Test
2. The memory test starts and the results of the test are shown.
Memory Test
Program No : 08501193-01
Boot
ROM
SRAM
DRAM
CPU RAM : OK
EEPROM : OK
Battery
The contents of the checking are shown below.
- Memory Test:
SRAM (Backup)
CPU RAM
EEPROM
- Battery:
When the test is performed, the voltage of the backup battery BT1 is checked
and displayed. When a battery is newly installed, the voltage reads about +3.3
VDC. If the Status display field shows
voltage has dropped below +2.5 VDC. When this occurs, replace the battery
with a new one. When the battery voltage goes down below +1.8 VDC, it
becomes impossible to back up the storage memory of received messages
(U10: SRAM). In this case, received messages are deleted when the power is
turned off.
: BOOTPGN-00
: OK
: OK
: OK
: OK (3.3V)
Hit any key
Memory
ROM built-in U8
DRAM
built-in U8
BT1
CR2450 F2ST2L
U8
Main CPU
BAT CHECK
BAT VOL
Fig. 7.1.1 Backup Battery voltage detection circuit
Check on checksum
U10
U5 Checked by Read/Write test
U13 Checked by Read/Write test
mark, it shows that the battery
Reset IC
J7 RES N
SRAM Vcc
U11
CE1 N
1 2
Q9
Q6
7-2
7.1 Self Test
Check on
U10
SRAM