Epson Research and Development

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REG[13h] Screen 2 Display Start Address Register 0

Start Address

Start Address

Start Address

Start Address

Start Address

Start Address

Start Address

Start Address

Bit 7

Bit 6

Bit 5

Bit 4

Bit 3

Bit 2

Bit 1

Bit 0

 

 

 

 

 

 

 

 

 

 

 

 

 

REG[14h] Screen 2 Display Start Address Register 1

 

 

 

 

 

 

 

 

 

 

 

 

Start Address

Start Address

Start Address

Start Address

Start Address

Start Address

Start Address

Start Address

Bit 15

Bit 14

Bit 13

Bit 12

Bit 11

Bit 10

Bit 9

Bit 8

 

 

 

 

 

 

 

 

 

 

 

 

 

REG[15h] Screen 2 Display Start Address Register 2

 

 

 

 

 

 

 

 

 

 

 

 

n/a

n/a

n/a

n/a

Start Address

Start Address

Start Address

Start Address

Bit 19

Bit 18

Bit 17

Bit 16

 

 

 

 

 

 

 

 

 

 

 

 

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.

4.3.2 Examples

Example 7: Display 380 scanlines of image 1 and 100 scanlines of image 2. Image 2 is locat- ed immediately after image 1 in the display buffer. Assume a 640x480 display and a color depth of 1 bpp.

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.

Programming Notes and Examples

S1D13504

Issue Date: 01/02/01

X19A-G-002-07

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Image 167
Epson S1D13504 manual REG13h Screen 2 Display Start Address Register, REG14h Screen 2 Display Start Address Register