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Sharp MZ-3500 service manual Character Vram select circuit, Blsc

Models: MZ-3500

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MZ3500

4-10. Character VRAM select circuit

 

 

 

The signal BLNK is used to address the ASCII RAM

Lov*/ when

6 1 1 6( 2 K * 8 )

* 0 0 0 0

within address area of 0000-07FF in transferring

0300^07FF

ASCB

- 07PF

the display data from the VRAM to the CG.

CS

V-RAM

 

 

2 1 1 4 ( ! K x 4 )

* 0 0 0 0

First half of

-03FF

attribute

2 1 1 4 ( 1 K * 4 )

Latter half of

# 0 4 0 0

- 07FF

attribute

 

#0000

 

-07FF

BL'SC

BLNK Erase signal

TTJ Period that the GDC is enabled to read/write and draw graphic data.

H-SYNC TT_

BLANK

[Circuit description]

With respect to GCD1, the assignment during read/write

of the character VIDEO-ROM is per the table below. The

character VRAM select circuit is provided. Jo accomplish this function.

 

 

Latter half of

 

 

*07FF

6 I 1 6 > 2 K » 8

)

 

 

 

attribute

 

t

 

 

 

 

*0400

ASL C

 

 

ARIO = H1

 

First half

 

T

#03KF

 

 

 

V - K A M

 

 

 

 

of attribute

AK10

 

 

 

 

= Low toooo

8bil

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Page 42
Image 42
Sharp MZ-3500 service manual Character Vram select circuit, Blsc
Page 41 Page 43