PCA84C646P PHILIPS [NXP Semiconductors], PCA84C646P Datasheet - Page 22

• Manufacturer Part Number: PCA84C646P
• Description: Microcontrollers for TV tuning control and OSD applications
• Manufacturer: PHILIPS [NXP Semiconductors]

Philips Semiconductors
10.2
Three Derivative Registers are used to address and load
data into the display RAM. These registers (configurations
are shown in Tables 18, 19 and 20) are described in the
following Sections.
10.2.1
Table 18 DCRAR (address 30H)
This is Derivative Register 30 and bits <5-0> holds the
address of the location in display RAM to which the data
held in registers DCRTR and DCRCR will be written to.
Bits <7-6> are reserved.
10.2.2
Table 19 DCRTR (address 31H)
This is Derivative Register 31 and holds the character font
attribute data. The data will be loaded into bits <3-0> of the
location in RAM pointed to by the contents of DCRAR.
Bits <7-4> are reserved.
10.2.3
Table 20 DCRCR (address 32H)
This is Derivative Register 32 and holds the character data
that will be loaded into bits <9-4> of the location in RAM
addressed by the contents of DCRAR. Bits <7-6> are
reserved.
10.3
1. Select the start address in display RAM. The start
1995 Jun 15
Microcontrollers for TV tuning
control and OSD applications
7
7
7
address is stored in DCRAR and can take any value
between 0 and 63.
Loading character data into display RAM
Writing character data to display RAM
DCR A
DCR A
DCR C
6
6
6
DDRESS
TTRIBUTE
HARACTER
C5
A5
5
5
5
C4
A4
R
4
4
4
R
EGISTER
R
EGISTER
EGISTER
A3
C3
T3
3
3
3
(DCRAR)
(DCRTR)
(DCRCR)
A2
C2
T2
2
2
2
A1
C1
T1
1
1
1
A0
C0
T0
0
0
0
22
2. Load the character attributes into DCRTR. If the
3. Load the character data into DCRCR. This operation
Overflow of the DCRAR, i.e. overflow from 63 to 64,
makes it reset to zero. After the instruction ‘MOV D32H, A’
is finished, the post-increment operation is performed
automatically. Auto-post-increment operation:
After master RESET the initial values of DCRAR, DCRTR
and DCRCR are all zero. Figure 16 shows how DCRAR is
incremented and advanced.
10.4
The default values of the display characters, after master
RESET, are as follows:
If another set-up is needed, the first character should be
SP code and second character is CR code to define the
character size and background colour.
handbook, halfpage
Begin
End
Background colour = Blue (R = 0, G = 0, B = 1)
Character size = 1V/1H
End-of-Display control bit = 0.
DCRAR
attributes of a series of displayed characters are the
same, only DCRCR needs to be updated.
The meaning of the attributes (4 bits) is dependent on
the contents of the next command (the data in the
DCRCR bits <5-0>; i.e. Carriage Return Code, Space
Code or Character Font Code).
loads the selected RAM location with the data held in
registers DCRTR and DCRCR. The address held in
DCRAR is then incremented by ‘1’ pointing to the next
RAM location in anticipation of the next operation.
(DCRAR)
If (DCRAR) > 63 then (DCRAR)
Default value of the display character
63
00
Fig.16 DCRAR increment cycle.
PCA84C646; PCA84C846
(DCRAR) + 1
01
62
02
61
03
04
Preliminary specification
0
19
MED208
17
18