ER-A440 (serv.man4). ERA440 Service Manual - Sharp ECR Service Manual (repair manual). Page 17

This circuit monitors +24V supply voltage.

The voltage at the (–) pin of the comparator IC3A is always main-
tained to 5.1V by means of the zener diode ZD2, while +24V supply
voltage is divided through the resistors R12, R13, and R14, and is
applied to the (+) pin. When normal +24V is in supply, 6.8V is sup-
plied to the (+) pin, therefore, signal POFF is at a high level. When
+24V supply voltage decreases due to a power off or any other
reason, the voltage at the (+) pin also decreases. When +24V supply
voltage drops, the voltage at the (+) pin drops below +5.1V, which
causes POFF to go low, thus predicting the power-off situation.

The STOP signal from the CPU is converted into the RESETS signal
by the CKDC6.

The  RESETS signal from the CKDC8 is converted into the RESET
 signal at the gate backed-up by the VRAM power, performing the
system reset.

Fig. 5-1

( 1)  “Internal I/O” means the registers in the H8/510.

( 2)  “External I/O” means the base system I/O area to be ad-

dressed in page 0. 

( 3) "Memory image area" means the lower 32KB of ROM area

which is projected to 000000H ~ 007FFFH for allowing reset
start and other vector addressing, or the lower 32KB of RAM
area which is projected to 008000H ~ 00FE7FH for allowing 0
page addressing of work RAM area. 

( 4)  “Expansion I/O” means expansion I/O device area which isad-

dressed to area other than page 0.

Fig. 5-2

•

ROM image area: Image is formed in ROM area address
C00000H to C07FFFH. This area is identical to IPL ROM area
which will beseparately developed. 

•

RAM image area: Image is formed in RAM area address 1F0000H
to 1F7E7FH. ( Note)  

Note:  Image can be formed in lower 32KB of RAS2.

Fig. 5-3

RESETS

STOP

CKDC8

RAS3

  4

  5

6

IC10B
74HC00S

/(RAS3./RESET)

/RESET

  1

  2

3

IC10A
74HC00S

VDD

C86
1000P

C87
1000P

R123

10K

C88
1000P

 9

10

8

14

IC10C
74HC00S

14

14

VDD

VDD

Internal I/O
External I/O
Memory image area

(*1)
(*2)
(*3)

RAM area
(10M byte)

ROM area
(3M byte)

Expansion I/O area (1M byte)

000000H

1C0000H

C00000H

FFFFFFH

000000H

004000H

008000H

00FFFFH

1FFFFFH

ROM image area
32KB

RAM image area
slightly smaller than32KB

NOT USE

00F800H

00FE80H

00FF80H

00FFFFH

RAM image area

Internal I/O area

External I/O area
(0 page)

1BFFFFH

RAM area

C00000H

D00000H

EFFFFFH

ROS3

NOT USE

  ROS1
(256K Byte)

C40000H

CA0000H

    ROS2
(Not used)

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