Tandy 1000 Technical Reference Manual

Tandy 1000
Technical Reference Manual
MC6845
TABLE 3 - Typical 80 x 24 Screen Format Initialization of CRTC
Programmed Value
Reg. # Register File
Program
Calculation·
Unit
RO H Total
T
c
102 •. 527 ~ 53.76 ~s
Rl H Displaved
T
c
80 •. 527 ~ 42.16 ~s
R2
H Sync Position
T
c
86 •. 527 ~ 45.32 ~s
R3 H Sync Width
T
c
9 •. 527 ~
4.74~s
R4 V Total T
cr
25. 645.12 ~ 16.13 ms
R5 V Total Adjust
Tsr
10.53.76
~
54ms
R6
V Displayed
T
cr
24. 645.12 ~ 15.48 ms
R7
V Sync Position T
cr
24. 645.12 ~ 15.48 ms
R8
Interlace Mode
R9 Max Scan Line Address
Tsl
RIO Cursor Start
Tsr
Rll Cursor End
Tsl
R12 Start Address (H)
R13
Stan Address (L)
R14 Cursor (H)
R15 Cursor III
Decimal
102 - 1 ~ 101
80
86
9
25~1~24
10
24
24
11
o
11
12B
128
He.
Nhl ~ S65
Nhd ~ S50
Nhsp
~ S56
Nhsw
~ S09
N
VI
~ S18
Nadi
= SOA
Nvd = S18
N
vsp
= S18
SOO
Nsl = S08
Soo
SOB
SOO
S80
SOO
S80
Clock Period '=' T c = .527 loiS
Scan Line Period = T sl = (Nht + 1) x T c = 102 x .527 loiS = 53.76 loiS
Character Row Period = T cr:: Nsl x T sl = 12)( 53.76jJs = 645.12 IJS
aThese are typical values for the Motorola M3000 Monitor; values may vary for other monitors.
FIGURE 12 - INITIALIZATION OF CRTc FOR 80x24 SCREEN FORMAT IN TABLE 3
CLERR COUNTER
CR TC RDOR REG
RCC TO CRTC REG
INC COUNTER
LRST CRTC l"EG?
$213
$65 .. $50 .. $56 .. $9
$18., $1.'IR .• $/ .9.' $/S
0 .. UtB .. 0 .. $08
$81:1 .. $81:1
#:t113
CRTI I
CRTHIT
$l'l
#$20
$9081:1
0 ... .",·
$91:18/
0828
NRN
ORG
CLR E:
LOX
STA 8
LOR A
STR A
!NX
INC 8
CNP B
8NE
Stu
ORG
CRTTRB FCB
FCB
FCB
FOB
END
09213
981:10 CRTI I
09
901:1/
CRTINT
5F
CE
F7'
A6
87
138
5C
CI Ie
26 F2
3F
65
I c-
oo
08se
08013
1:1884 CRTTRB
0898
08813
el'l81
Oill:14
Bl'lO?
1:1809
OOOC
1:18130
01:18E
1:18/l'l
9l'l12
1:1821:1
09213
1:1924
8828
082C
PAGE 081
08881
00002
08883
01:1('184
1:10085
00l'll'l6
00807'
Ol'lOOS
OOt109
00l'l18
1:1801/
00012
08813
l'll'll'l14
1:188/5
00016
08017'
l'lOel8
CRTII
TOTAL ERRORS 088013
® MOTOROLA Semiconductor Products Inc.

Tandy 1000 Specifications

General

Processor	Intel 8088
Processor Speed	4.77 MHz
RAM	128 KB (expandable to 640 KB)
Operating System	MS-DOS 2.11
Manufacturer	Tandy Corporation
Release Year	1984
Storage	Single or double 5.25" floppy disk drive (360 KB), optional hard drive
Sound	Tandy 3-voice sound
Ports	Parallel, Serial
Graphics	CGA (Color Graphics Adapter)
Graphics Modes	320x200, 640x200