ER-A460 (serv.man2). ERA460 470 Service Manual - Sharp ECR Service Manual (repair manual). Page 37

1

Key operation

120 

→

 TL 

2

Functional description
Perform the following check for the standard RAM 32 KByte
SRAM. The memory contents should not be changed before and
after the check.

Perform the following processes for  memory address to be
checked (1C0000H~1DFFFFH).
PASS1: Save memory data.

PASS2: Write data "0000H."
PASS3:  Read and compare data "00H," write data "55H."
PASS4:  Read and compare data "55H," write data "AAH."
PASS5: Read and compare data "AAH."
PASS6: Restore the memory data.

If a compare error occurs in the check sequence PASS1-PASS6,
an error print is made. If no error occurs through all address, the
check ends normally.

The following address check is performed further.
Check point address = 1C0000H, 1C0001H

1C0002H, 1C0004H
1C0008H, 1C0010H
1C0020H, 1C0040H
1C0080H, 1C0100H
1C0200H, 1C0400H
1C0800H, 1C1000H
1C2000H, 1C4000H
1C8000H, 1D0000H

S

R A M

T S

S R V

DOT DISPLAY:

7-SEGMENT DISPLAY:

Initialize the table pointer

Read check address from the
address table by pointer
sccess

Save data of check address
to the CPU register

Write data 55H to check
address

For check address other than
the current check address,
write AAH after saving 1-byte
data into the register

Is the

current check

address 55H?

Reset operation of saved data

Is the

operation comleted

for the other check

address?

Revise the table pointer

Is the

address table

completed?

End

YES

YES

YES

NO

Address
error

NO

NO

Check address
table

START

Table pointer

END

Operation flow

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