Kramer Electronics VP-790 - Manual (Page 6)

2 VP-790 Protocol - Communication
The data to be sent is (hex):
53 41 50 01 FF FF FF FF 00 00 00 20 00 00 00 00
54 50 01 00 00 00 00 00 00 00 00 10 00 00 00 00
50 46 00 68 00 00 00 00 00 00 00 04 7F FF FF FF
1.2 Handshake
All API calls (and API returns) are acknowledged by the RS232 receiver with the
following (logical header only) (hex):
73 61 50 01 FF FF FF FF 00 00 00 00 00 00 00 00
1.3 API Return
The acknowledgement is followed by the API return. This return has the same
structure as a call, first a 16 byte logical header, followed by a 16 byte application
header, followed by the data package of variable length. The logical header is for
an API return is (hex):
53 41 50 01 FF FF FF FF ww xx yy zz 00 00 00 00
ww xx yy zz is the payload size (type UWORD32) of the following transmission in
bytes (application header size (16 bytes) + data package size of variable length).
The application header is (hex):
74 50 01 00 00 00 00 00 ww xx yy zz 00 00 00 00
ww xx yy zz is the payload size (type UWORD32) of the following transmission in
bytes (data package size of variable length).
The data package returns the parameter values (hex):
70 46 uu vv 00 00 00 00 ww xx yy zz data
uu vv is the Index (type UWORD16) of the API that has been called. ww xx yy zz is
the size of the parameter data buffer. The first byte of the data is the return value of
the function -here: always a 1 byte error code -, followed by the values of all
(Output) parameters. The ordering has to be matched with the API prototype
parameter ordering and size.