EF9345 Datasheet, PDF (35/38 Pages) STMicroelectronics – HMOS2 SINGLE CHIP SEMI-GRAPHIC DISPLAY PROCESSOR

EF9345
Notes on Command Execution
1. The execution of any command starts at the
trailing edge of DS when (and only when) :
- EF9345 has been selected,
- XQR has been set,
at the previous AS falling edge.
This scheme allows loading a command and its
argument in any order. For instance, a command,
once loaded,may be re-executed with new or partly
new arguments.
2. At power on, the busy state is undeterminated.
It is recommanded to load first a dummy
command with XQR = 1 before any effective
command.
3. While Busy is set, the current command is
under execution. Register access is then
restricted.
Register access with XQR = 0
- Read STATUS is effective.
- Write COMMAND or any other register access
are ineffective.
That is to say, the microprocessor reads undeter-
mined values and may not modify a register.
Register access with XQR = 1
- Read STATUS or write COMMAND are effective,
- Access to other registers is ineffective.
However, the previous command is aborted and
the new command execution launched (with an
initial state undetermined for registers and memory
locations handled by the aborted command).
4. Execution suspension
The execution of any command (except VRM,
VSM) is suspended during the last and first TV line
of an active row. This is because the memory bus
cannot be allocated for microprocessor access dur-
ing this 104 µs period.
This holds too for internal resource access because
on-chip data transfer uses internal data memory
bus.
IND Command (See Figure 37)
This command transfers one byte between R1 and
an internal resource. The r parameter designates
one on-chip indirect register.
Fixed Format Character Code Access :
KRF, KRG, KRL, KRC
Each of these commands is dedicated to transfer
one complete character code between DATA reg-
isters and memory. MP is exclusively used.
KRF transfers 24 bits.
KRG transfers 16 bits
KRL transfers 12 bits.
KRC transfers 8 bits.
Code packing, pointer and data structures are ex-
plained in the corresponding character code sec-
tion.
When auto-incrementation is enabled, MP is auto-
matically updated after access so as to point to the
next location. This location corresponds to the next
right position on screen. When last position (X = 39)
is accessed, LXm is set. When last position is
accessed with auto-incrementation, alarm is also
set. MP is then pointing back at the beginning of
the row : there is no automatic Y incrementation.
Variable Code Handling Commands :
KRV EXP, CMP, KRE
An overview on these commands is given in ”han-
dling the variable codes” (40 char./row section).
KRV uses R5 to point the attribute file. LX_a is set
when this file is full (the last attribute pair has been
accessed).
EXP and CMP use MP and R5 in the same way as
KRV. Furthermore, R4 points to a working double
buffer. Thse two commands process a whole row
buffer and stop either at the end of the row buffer
or when the file overflows. In the last case, the
alarm bit is set.
KRE uses MP to point to a buffer and R4 to point
to a working double buffer. R5 is unused. In other
respects, KRE is identical to KRL.
For these commands, R4(5:7) hold the LSB’s block
dress of the working buffer W.
Figure 38
76543210
Z₀ Z₁ Z₂
Y
R4
ZW
YW
ZW₃ is given by bit 6 of R6
35/38