Epson S1D13504 ユーザーズマニュアル

Page 29

Vancouver Design Center

Programming Notes and Examples

S1D13504

Issue Date: 01/02/01 

X19A-G-002-07

These three registers form the twenty bit offset to the first word in display buffer that will be shown 
in the screen 2 portion of the display.

Screen 1 memory is always the first memory displayed at the top of the screen followed by screen 
2 memory. However, the start address for the screen 2 image may in fact be lower in memory than 
that of screen 1 (i.e. screen 2 could be coming from offset 0 in the display buffer while screen 1 was 
coming from an offset located several thousand bytes into display buffer). While not particularly 
useful, it is possible to set screen 1 and screen 2 to the same address.

1.

The value for the line compare is not dependent on any other setting so we can set it immedi-
ately (380 = 0x17C).

Write the line compare registers [0Fh] with 0x01 and register [0Eh] with 0x7C.

2.

Screen 1 is coming from offset 0 in the display buffer. Although not necessary, ensure that the 
screen 1 start address is set to zero.

Write 0x00 to registers [10h], [11h] and [12h].

3.

Calculate the size of the screen 1 image (so we know where the screen 2 image is located). 
This calculation must be performed on the virtual size (offset register). Since a virtual size was 
not specified assume the virtual size to be the same as the physical size.

offset = pixels_per_line / pixels_per_word = 640 / 16 = 40 words per line

screen1_size = offset * lines = 40 * 480 = 19,200 words = 0x4B00 words

4.

Set the screen 2 start address to the value we just calculated.

Write the screen 2 start address registers [13h], [14h] and [15h] with the values 0x00, 0x4B 
and 0x00 respectively.

Start Address 

Bit 7

Start Address 

Bit 6

Start Address 

Bit 5

Start Address 

Bit 4

Start Address 

Bit 3

Start Address 

Bit 2

Start Address 

Bit 1

Start Address 

Bit 0

Start Address 

Bit 15

Start Address 

Bit 14

Start Address 

Bit 13

Start Address 

Bit 12

Start Address 

Bit 11

Start Address 

Bit 10

Start Address 

Bit 9

Start Address 

Bit 8

n/a

n/a

n/a

n/a

Start Address 

Bit 19

Start Address 

Bit 18

Start Address 

Bit 17

Start Address 

Bit 16