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SMSC

CRT9021B Datasheet Preview

CRT9021B Datasheet

CRT Video Attributes Controller

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STANDARD MICROSYSTEMS
CORPORATIO~N~_ _•
CRT9021B
J,1PC FAMILY
CRT Video Attributes Controller
VAC
FEATURES
o On chip video shift register (28.5 MHz max.)
o On chip attributes logic
Reverse video
Character blank
Character blink
Underline
Full/half intensity
o Four modes of operation
Wide graphics
Thin graphics
Character mode without underline
Character mode with underline
o On Chip logic for double height/double
width characters
o Accepts scan line information in parallel
or serial format
o Four cursor modes dynamically selectable via 2
input pins
Underline
Blinking underline
Reverse video
Blinking reverse video
o Programmable character blink rate
o Programmable cursor blink rate
PIN CONFIGURATION
D0 1
MS0 2
MS1 3
REVID 4
CHABL 5
BLINK 6
INTIN 7
+5V 8
ATTEN 9
INTOUT 10
CURSOR 11
RETBL12
LD/SH 13
VIDEO 14
28 D1
27 D2
26 D3
25 D4
24 D5
23 D6
22 D7
21 VSYNC
20 GND
19 SL0/SLD
18 SL1/SLG
17 SL2/BLC
16 SL3/BKC
15 VDC
PACKAGE 28-pin D.I.P.
o On chip data and attribute latches
o + 5 volt operation
o TTL compatible
o MOS n-Channel silicon gate COPLAMOS® processM
o Compatible with CRT 5037 VTAC®; CRT 9007 VPAC
GENERAL DESCRIPTION
The SMC CRT 9021 Video Attributes Controller line, reVerse video character block, and blinking
(VAC) is an n-channel COPLAMOS MOS/LSI device reverse video character block. When used in the serial
containing Graphics logic, attributes logic, data and scan line input mode, the cursor mode may be selected
attributes latches, cursor control, and a high speed via two input pins. When used in the parallel scan line
video shift register. The CRT 9021 , a character gen- input mode, the cursor mode is a mask program option
erator ROM and a CRT controller such as the CRT and is fixed at the time of manufacture.
9007 provide all of the major circuitry for the display
Two graphics modes are provided. In the wide
portion of a CRT video terminal.
graphics mode, the CRT 9021 produces a graphic
The CRT 9021 serial video output may be con- entity the size of the character block. The graphic entity
nected directly to a CRT monitor's video input. The contains eight parts, each of which is associated with
maximum video shift register frequency of 28.5 MHz one bit of the input byte, thereby providing 256 unique
allows for CRT displays of up to 132 characters per graphic symbols. The thin graphics mode enables the
data row.
user to create thin line drawings and forms.
The CRT 9021 attributes include: reverse video,
In both graphics modes, continuous horizontal and
underline, character blank, character blink, and full/ vertical lines may be drawn. Additional flexibility is
half intensity selection. In addition, when used in con- provided by allowing the mask programming of the
junction with theCRT9007VPAC;M the CRT 9021 will placement and dimensions of the blocks or lines within
provide double height or double width characters.
a character block. In the thin graphics mode, mask
Four programmable cursor modes are provided on programming allows serrated horizontal or vertical
the CRT 9021. They are: underline, blinking under- lines.
281
I




SMSC

CRT9021B Datasheet Preview

CRT9021B Datasheet

CRT Video Attributes Controller

No Preview Available !

07-00
CURSOR
RETBL
WISH
ATIEN
MSO
MSI
REVIO
CHABL
BLINK
INTIN
ATTRIBUTE
AND
GRAPHIC
LOGIC
RO/SLD
R1/SLG
R2/BLC
R3/BKC
J--------- VIOEO
~--------- VOC
L
A
T 1 - - - - - - - - - - + INTOUT
C
H
FIGURE 1: CRT 9021 BLOCK DIAGRAM
DESCRIPTION OF PIN FUNCTIONS
PIN NO. NAME
1,28,27,26, Data
25,24,23,
22
SYMBOL
D7-DO
2 Mode Select 0 MSO
3
Mode Select 1
MS1
4 Reverse Video REVID
5 Character blank CHABL
6 Blink
BLINK
7 Intensity In
INTIN
FUNCTION
In the character mode, the data on these inputs is passed through the Attributes
logic into the 8 bit high speed video shift register. The binary information on D7
will be the first bit output after the LD/SH input goes low.
In the thin or wide graphics mode these 8 inputs will individually control the onloff
condition of the particular portion of the character block or line drawing. Figures 2
and 3 illustrate the wide and thin graphics modes respectively and their
relationships to D7-DO
These 2 inputs define the four modes of operation of the CRT 9021 as follows:
MS1, MSO = 00; Wide graphics mode
= 10; Thin graphics mode
= 01; Character mode without underline
= 11; Character mode with underline
See section entitled Display Modes for details.
When this input and Retrace Blank (RETBL) are both low, data from the
Attributes and Graphics logic is presented directly to the video shift register.
When this input is high and RETBL is low, the Attribute and Graphics logic will
invert the data before presenting it to the video shift register.
When this input is high, the parallel inputs to the video shift register are all set low
(or high depending on the state of REVID) thus providing a constant video level
for the entire length of the character block.
When this input is high and both the RETBL and CHABL inputs are low, the char-
acter will blink at the programmed character blink rate. Blinking is accomplished
by causing the video to go to the background level during the "off" portion of the
Character Blink cycle. This video level may be either the white or black level
depending on state of REVID. The duty cycle for the character blink is 75/25 (ani
off). This input is ignored if it coincides with the CURSOR input and the cursor is
formatted to blink.
The INTIN input along with the INTOUT output provides a user controlled general
purpose attribute. Data input to INTIN will appear at INTOUT with the same delay
as that from any other attribute input to the serial video output (VIDEO). By using
an external mixing circuit, it is possible to raise or lower the voltage level of the
video output to produce such attributes as "half intensity" or "intensity".
282


Part Number CRT9021B
Description CRT Video Attributes Controller
Maker SMSC
Total Page 12 Pages
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