Epson 5000 - Manual (Page 111)

Handshake timing
When the vacant area for data in the input buffer drops to 256
bytes, the printer outputs an X-OFF code or sets the DTR flag
to 1 (MARK) to indicate that it cannot receive data. When the
vacant area for data in the buffer increases to 528 bytes, the
printer outputs an X-ON code or sets the DTR flag to 0
(SPACE) to indicate that it is ready to receive data.
Error handling
When the printer detects a parity error, it prints an asterisk (*)
The printer ignores all other errors, including framing and
overrun errors.
Using Printer Options 4-19