Epson ES-1000C Reference Manual page 108

The color image data is sent as a set of three primary color pages.
1 ESC G command
2 Data block (image data for one block)
3 ACK code
4 Last data block (last line of each color page)
Steps 2 and 3 should be repeated for the number of lines (minus
1) specified for each color page of green, red, and blue until the
last data block is encountered.
Do not send the ACK code after the last data block of each color
page.
Color line sequence mode (one pass scanning)
The color image data is sent as one page, and three primary colors are
sent for each line.
1 ESC G command
2 Data block (image data for one line)
3 ACK code
4 Last data block (last line of the page)
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Command Reference