UPD17068 Datasheet, PDF (254/341 Pages) NEC – 4-BIT SINGLE-CHIP MICROCONTROLLER CONTAINING IMAGE DISPLAY CONTROLLER AND PLL FREQUENCY SYNTHESIZER FOR DIGITAL TUNING SYSTEMS

µPD17068
Table 16-9 Hardware Affected by Index Modification
VRAM address after
index modification
VRAM bank VRAM address
1, 5, 9, D
2FH
30H to 32H
33H
34H to 3FH
3, 7, B
34H to 3FH
Affected hardware
Bank
2
2
2
—
—
Address
6FH
70H to 72H
73H
74H to 7FH
74H to 7FH
Hardware name
Port 2D
Ports 2A-2C
VRAM bank specification
System registers
System registers
Caution Actually, there is no VRAM at VRAM addresses 30H to 3FH. Do not execute an instruction that
operates these addresses.
When an index register increment instruction is executed, in particular, the VRAM addresses may become
30H to 3FH. When setting data over multiple VRAM banks by using an increment instruction, proceed as
follows:
(1) Increment the VRAM address. When the address reaches 2FH, stop incrementing and clear the IXE
flag.
(2) Switch the VRAM bank and reset the index register.
(3) Set the IXE flag again and start incrementing.
& When the memory pointer is used to write data to the VRAM, ports and system registers may be
operated in the same way as when index modification addressing is used. The hardware that is
affected is the same as that shown in Table 16-9. However, since VRAM addresses 30H to 3FH are
not VRAM area, do not set them in the memory pointer.
When accessing address 2FH of VRAM banks 1, 5, 9, and D, do not use the memory pointer, but write
data with a direct memory operation instruction.
( Always set control data 1 at the beginning of a line and a screen whether or not the data is to be
changed.
) Set the character pattern selection data sequentially from the VRAM low address, in the order
displayed from the top left of the screen.
* Always set the line carriage return data at the end of a line.
+ Always set the VRAM pointer reset carriage return data at the end of the VRAM data when data
exceeding the VRAM capacity (extended display mode) is displayed by program.
, Always set the screen carriage return data at the end of the data of a screen.
- When displaying data in the extended display mode, before reading the VRAM pointer reset carriage
return data, rewrite the VRAM data at the first line that exceeds the VRAM capacity.
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