Sharp MZ-3500 service manual CG Address Select Circuit, Structure

4 8 CG Address Select Circuit

ASCII	C.G. Structure
» I i r r
=^=^
1020
10! 1-
	Character
leBytes	Code	01
	For
			8 x 1 6 dot
	Model 3500
			> Pattern
lOOh			400 Rasters
	Character
ifiBytes	Code	00
	For

Model 3500	I
1000	\ l'=	I -
01-1^	M'-O	•>

I

==

0020

001 t		Code	01			8x8 Dot
a Bytes					I
		For				> Pattern
0018		Model 3200			A3=l	200 Rasters
0017	'/	'///' s/	/////^		f
K Bytes '		Code	01 ',
	'	For	x
(Hi in	,. Model 3500:				\ 1-0
001 1		Character			*
8 Bytes		Code	00
					1
		For			\ i i
0 Iftk		Model 3200
O K I	/	Character		/i	t
fc Bytes'		Code	00	',
		For		<l
ii i		^Model 3500^			M
i in			i

8 b ts

M "

When 200 rasters on ASCII in use

(only the high order 8 bytes of 16 bytes are set to low level I

ASCII character structure of the 200 raster CRT

ASCII characterstructure of the 400 raster CRT

[Circuit description] (Purpose)

The character genrerator (CG) incorporates all character code^ used by the 200 raster video display unit of the \X 3500 and by the 400 raster video display unit of the \X 3500 The CG address select cirruit is therefore used to select those modes

[Operational description]

1When the 400 raster CRT is in use, RA40 is set to high level which sets A12 of the CG to high level at all times, so that the CG address above 1000 is selected Also, gate (1) opened so that LC3 is input to A3 of the CG At the same time, gate (3) is opened so that the gate of the LS240 is closed every 16 bytes

2When the 200 raster CRT is in use, RA40 is set turned to low level which sets A12 of the CG to low level continuously, so that the CG address 0000 OFFF is selected Also, gate (2) is opened so that the

CPU

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