DEC VT220 Technical Manual page 107

characters
(ROM space
data) .
(CRM0-CRM3l) packed one character per each 5 data rows
not taken up by character font data is filled with FFH
Figure 6-19 shows that each of the 256 characters packed one
character per data row consist of 10 bytes of data, one byte for
each scan line of the character. When addressing one of these
characters, a single base address is provided to the character ROM
by character latch 2, and each of the 10 scan lines is addressed
by the address mux input.
However, addressing the remaining 32 characters (CRM0-CRM31)
requires a separate base address input from character latch 2 for
every two scan lines of the character to be processed. Figure 6-20
shows that each of the
32
characters packed into five different
data rows consist of 10 bytes of data, one byte for each scan
line, but only two bytes per data row.
Later in this chapter, Table 6-2 describes the signals shown in
Figure 6-17.
SCAN LINE
ADDRESS
C
PPLEMENTAL
ARACTERS
PACE
EV. QUESTION
RROR
HARACTERI
SCII
HARACTERS
M
HARACTERS
27-160)
EC
ECIAL
RAPHICS
HARACTERS
96-126)
.
BASE
I
su
I
SL2
I
SL3
I
SL41 SLS! SL6l SL7
I
SLsl SL91 SL10
ADDRESS
I
X~O
X=l X=2 X=3 X=4 X=5 X=5 X=7 X=B X=9
100X H/OOOX Hi
(CRM 32!
f-s
101 X H/OO;
x
H
f--
(SGC 961
-
; 02X H i 002X H,
103X H/003X H
~
(SGC 971
-
(SGC 98)
- D
104X Hi004X H
f--
(SGC 99)
SP
-
G
l;DX H/O;DX HE
C
-
(
(SGC 124)
-
11 EX H/O; EX H
F
(SGC 125)
-
l1FX H/01FX H
(SGC 126)
R
120X H/020X H (
(CRM 261
~(E
121 X H/02; X H
(CRM 331
};
122X H/022x H
I--
(CRM 34)
-
123X H!023X H
I--
(CRM 351
-
f -
-
17DX H/07DX H
I--
-
I -
(CRM 1251
-
17EX H/07EX H
(CRM 1251
1 7FX H/07FX H
(CRM 127)
lS0X H/OBOX H
f -
(CRM 1281
-
181 X H/081 X H
I--
(CRM 129)
-
I--
-
CR
C
19EX H/09EX H
I--
(CRM 1581
-
11
19FX H/09FX H
I--
(CRM 1591
-
1AOX H/OAOX H
I--
(CRM 150)
-
1A1 X H/OA 1X H
(CRM 151)
I--
-
1A2X H/OA2X H
(CRM 162)
1 A3X HiOA3X H
I -
(CRM 153)
-
J"
I--
-
-=
SU
1 F8X HiOFBX H
F="
I -
(CRM 251) - CH
1FCX H/oFCX H
I--
(CRM 252)
-
1FOX HiOFDX H
(CRM 253)
1 FEX H/OFEX H
1FFX HiOFFX H
Figure 6-19 Character ROM Map: CRM32-255 and
Special Graphics
6-23