EF9345 Datasheet, PDF (20/38 Pages) STMicroelectronics – HMOS2 SINGLE CHIP SEMI-GRAPHIC DISPLAY PROCESSOR

EF9345
Random access to a variable code is obviously not
as easy. The EXP, KRE and CMP commands are
designed to facilitate this task (figure 17).
The EXP command translates a full row of variable
codes into a row of expanded codes. Expanded
codes are generally not displayable by very similar
to the long codes.
KRE gives a random access to an expanded code
and makes it appear as a regular long code.
The CMP command translates a full row of ex-
panded code into a row of variabble codes and
minimizes the file size in the process.
These commands use a buffer pair as working
area.
Figure 18 : Variable Codes in memory
KRV COMMAND
R1 ^C
R2 ^B
R3 ^A
R4
-
R5 BF, XF
R6 D, Y
R7 B, X
X
0
39
D district
number
B (even)
Y
BA
B + 1 = BF
XF :
file pointer
Fixed Short Codes
These fixed 16 bits codes achieve memory saving
by anotherway. They may be easier to handlethan
variable codes. The penalty is in lesser display
capabilities :
- Accentuated character sets are no longer avail-
able : accentuated characters must be individu-
ally provided by the character generators.
- G’11 and quadrichrome sets cannot be reached.
- Some attributes are latched and can be changed
only while displaying a space (delimitor code).
The KRG command allows an easy access from/to
an 80-byte row buffer in memory to/from the micro-
processor (Figure 19). Figure 20 gives the fixed
short to fixed long translation process which occurs
for each row - while loading the internal row buffer
before display.
Figure 19 : Fixed Short Codes in Memory 80
KRG COMMAND
R1 A*
R2 B*
R3 W
R4
-
R5
-
R6 D, Y ^Y
R7 B, X
X
0
39
District
A*
B (even)
B*
B+1
Overflow
buffer
B+2
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