TMPR3916 datasheet(89/225 Pages) TOSHIBA

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Chapter 3 Graphics Display Controller (GDC)

Preliminary

3-10

are not related to the address counter part (AC) but to this smooth scrolling feature. This leads to a

dot offset of 1 in the SS register part, so that the dot read as next is located at 0x50010025.

3.2.1.2

Scrolling Layers A and B

For working on layers A and B the application of smooth scrolling becomes a little more

difficult: One word contains data of four dots, of which the number can be coded by using just two

of the three bits reserved in SARx.

The algorithm shown in the following diagram is to be used:

newSARx = SARB

newSARx = SARA

MWRx = MWRA >> 15

MWRx = MWRB >> 15

LAYER_A

True

False

LEFT

True

False

newSARx = (newSARx & 0xfffffff8) | (preSARx & 0x00000003)

RIGHT

True

False

True

False

preSARx += offset

preSARx -= offset

preSARx += MWR * offset * 4

preSARx -= MWR * offset * 4

preSARx[2] !=

newSARx[2]

True

False

preSARx[2] !=

newSARx[2]

True

False

newSARx += 8

newSARx -= 8

SARB = newSARx

SARA = newSARx

LAYER_A

True

False

preSARx = newSARx & 0x00000007

newSARx += MWR * offset * 4

newSARx -= MWR * offset * 4

Example:

For scrolling a picture located at 0x50010024 (SARx: 0xA0020048) to the right by four dots do

the following:

newSARx = 0xA0020048

MWRx = 0x-------- (not needed for this example)

preSARx = 0x00000000

preSARx = 0xFFFFFFFC

newSARx = 0xA0020044

SARA = 0xA0020044

This new entry for start address register results in a physical bus address of 0x50010020, which

is the memory address located before the one read first in the last step. The smooth scrolling bits

show an offset of 0 so in the end the first dot read is located at 0x50010020, too.

Please be aware of the relationship of adding or subtracting the extra offset 0x08 to the scrolling

direction.

3.2.2

This scrolling type is implemented easily: Just change the values of the start and end registers in

horizontal and vertical direction using the projected dot offset:

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