Epson Research and Development
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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 1 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 10-4: 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
up to 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 started.
10.2.2 Color Expand BitBLT
This Color Expand BitBLT is similar to the Write BitBLT. It differs in that a bit set to 1 in
the source data becomes a pixel of foreground color. A source bit set to 0 is converted to a
pixel of background color. This function increases the speed of writing text while in
graphical modes.
This BitBLT operation includes several options which enhance its text handling capabil-
ities. As with the Write BitBLT, all data sent to the blit engine must be word (16-bit) writes.
The blit engine expands the low byte, then the high byte starting at bit 7 of each byte.
The start byte of the first WORD to be expanded and the start bit position within this byte
must be specified. The start byte position is selected by setting source address bit 0 to 0 to
start expanding the low byte or 1 to start expanding the high byte.
Programming Notes and Examples
Issue Date: 01/02/06
S1D13506
X25B-G-003-03
EPSON [ EPSON COMPANY ]
