Y108540-8
Service Manual
4-21
Fig. 4-20
PROBLEM
CORRECTIVE ACTION
Memory backup does
Check the voltage at point (1) indicated in the previous figure.
not work.
•
If the reading is almost the same as the battery voltage, replace the
mainboard.
•
If the reading is much less than the battery voltage or 0V, replace the
battery unit.
4.16 MEMORY CIRCUIT
A 512 Kbyte S-RAM (BS62LV4005) used as an external RAM for the PLUs, electronic journals, etc.
Multiplex bus P70 through P77 consists of data bus (D0-D7).
Multiplex bus P40 through P47 consists of data bus (A0-A7).
Multiplex bus P50 through P53 consists of data bus (A8-A11).
Multiplex bus P54 through P57 consists of data bus (A12-A15)
Multiplex bus P10 consists of data bus (A16).
Multiplex bus P11 consists of data bus (A17).
Multiplex bus P12 consists of data bus (A18).
P30 is used for chip select at RAM.
P31 is used for Output Enable.
P32 is used for Write Enable control.
A7
A6
A5
A4
A3
A2
A1
A0
A12
A13
A15
A14
A8
A16
A9
A11
A10
C70
0.1uF
VBB
VBB
1
2
3
4
5
6
7
8
9
RM2
10Kx8
D0
D1
D2
D7
D6
D5
D4
D3
A18
RAM_CS#
RD#
WR#
A0
12
A1
11
A2
10
A3
9
A4
8
A5
7
A6
6
A7
5
A8
27
A9
26
A10
23
A11
25
A12
4
A13
28
A14
3
A15
31
A16
2
CE
22
A17/CE2
30
WE
29
OE
24
D0
13
D1
14
D2
15
D3
17
D4
18
D5
19
D6
20
D7
21
VCC
32
GND
16
A18/A17
1
BS62LV2001/4006SCP
A17
JP2
JUMPER
JP3
JUMPER
JP4
*JUMPER
SRAM
2M
4M
JP2
OPEN
CONNECT
JP3
CONNECT
CONNECT
JP4
OPEN
CONNECT
