Epson Research and Development
Page 83
Vancouver Design Center
10. Program the BitBLT Destination/Source Linear Select bits for a rectangular blit (Bit-
BLT Destination Linear Select = 0, BitBLT Source Linear Select = 0).
Start the blit operation and wait for the blit engine to start. REG[100h] is set to 80h,
then wait until REG[100h] bit 7 returns a 1.
11. Prior to writing all nWORDS to the Blit FIFO, confirm the Blit FIFO is not full
(REG[100h] bit 4 returns a 0). If the BitBLT FIFO Not Empty Status returns a 0 (the
FIFO is empty), write up to 16 WORDS. If the BitBLT FIFO Not Empty Status re-
turns a 0 and the BitBLT FIFO Half Full Status returns a 0 then you can write up to 8
WORDS. If the BitBLT FIFO Full Status returns a 1, do not write to the BitBLT FIFO
until it returns a 0.
The following table summarizes how many words can be written to the Blit FIFO.
Table 10-6: Possible Blit FIFO Writes
BitBLT Control Register 0 (REG[100h])
Word Writes
Available
FIFO Not Empty Status
FIFO Half Full Status
FIFO Full Status
0
1
1
1
0
0
1
1
0
0
0
1
16
8
less than 8
0 (do not write)
Note
The order of register initialization is irrelevant as long as all relevant registers are pro-
grammed before the BitBLT is initiated.
10.2.8 Transparent Move BitBLT in Positive Direction
The Transparent Move BitBLT in Positive Direction moves an area of the display buffer to
a different area of the display buffer. It allows for selection of a transparent color which is
not copied during the blit. This allows fast display of non-rectangular images. For example,
consider a source bitmap having a red circle on a blue background. By selecting the blue
color as the transparent color and using the Transparent Move Blit on the whole rectangle,
the effect is a blit of the red circle only.
The Transparent Move BitBLT may move data from one rectangular area to another, or it
may be specified as linear. The linear configuration may be applied to the source or desti-
nation. Defining the Move BitBLT as linear allows each line of the Move BitBLT area to
be placed directly after the previous line, rather than requiring a complete row of address
space for each line.
Note
The Transparent Move BitBLT is supported only in a positive direction.
Programming Notes and Examples
Issue Date: 01/02/06
S1D13506
X25B-G-003-03
EPSON [ EPSON COMPANY ]
