Parker ACR Series, Руководство программиста

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Parker Hannifin
Receiving
When receiving control prefix encoded data, a '#' character is
thrown away and causes the next character to be read from the
data stream. If the character is in the range of 0x3F to 0x5F, the
character is 'XORed' with 0x40 to decode the true value. Otherwise,
the character is used exactly as read from the stream.
High Bit Stripping
High bit stripping follows Kermit communications protocol
conventions for 7-bit data paths. The escape code for high bit
stripping is the '&' character and must be used in conjunction with
the control character prefixing described above.
High bit stripping is for cases in which a 7-bit data path must be used
for binary data transfer. This mode introduces a large overhead in
the transfer of binary data since over half of the bytes are
expanded to two byte sequences and several are expanded to
three bytes. If possible, an 8-bit data path should be used for binary
data transfer.
Transmitting
If the character to be sent is greater than 0x7F, the character is
'ANDed' with 0x7F and proceeded with the '&' character. Note that
the AND may result in a control code which must then handled by
control character prefixing. The original character may also need to
be sent with control character prefixing.
For example, if the character to be sent is 0xC2, the character is
transmitted as a "&B" string. ( 0xC2 AND 0x7F = 0x42 = 'B' ) As another
example, if character to be sent is 0x83, the character is transmitted
as the three character "&#C" string. ( 0x83 AND 0x7F = 0x03 (control
character) ) The special case where the character to be sent is the
'&' character is handled with the two character "#&" string.
Receiving
When receiving high bit encoded data, '#' characters are handled
as normal control character prefix sequences. If the received
character is neither a '#' nor a '&' character, the character is used
exactly as read from the stream.
If the received character is the '&' character, it is thrown away and
causes the next character to be read from the data stream. This
new character may be a '#' character, which will initiate control
prefix decoding sequence. The result is a value in the range of 0x00
to 0x7F, which is then 'ORed' with 0x80 to re-establish the high bit in
the data.
100 Programmer’s Guide