Apple Newton Programmer’s Newton 2.0 (for Newton 2.0) - Manual (Page 863)

C H A P T E R 2 4
Built-in Communications Tools
Serial Tool 24-5
An endpoint can include kPacket , kEOP , and kMore flags to control the sending
and receiving of framed (packetized) data with the framed asynchronous serial
tool. For more information on these flags, see “Sending Data” (page 23-11).
The following is an example that shows how to create an endpoint that uses the
framed asynchronous serial tool:
myFramedEP := {_proto:protoBasicEndpoint};
myOptions := [
{ label: kCMSFramedAsyncSerial,
type: 'service,
opCode: opSetRequired } ];
returnedOptions:= myFramedEP:Instantiate(myFramedEP,
myOptions);
The framed asynchronous serial tool uses the standard asynchronous serial tool
options, as well as two framing options, which are summarized in Table 24-3.
These options are described in detail in “Options for the Framed Asynchronous
Serial Tool” (page 21-29) in Newton Programmer’s Reference.
The default settings for the kCMOFramingParms option implement BSC framing,
as shown in Figure 24-1.
Figure 24-1 Default serial framing
Each packet is framed at the beginning by the 3-character SYN-DLE-STX header.
The packet data follows; if a DLE (escape character) occurs in the data stream,
Table 24-3 Summary of framed serial options
Label Value Use when Description
kCMOFramingParms "fram" Any time Configures data framing parameters.
kCMOFramedAsyncStats "frst" Any time Read-only option returns the number
of bytes discarded while looking for
a valid header.
Octet 1
SYN
Flag
0001011 DLE
Flag
0001000 STX
Flag
0000001 Message . . . DLE
Flag
0001000 ETX
Flag
0000001 Frame
Check
Sequence
2 3 . . . . . . . . . . . . . . . . . . N-3 N-2 N-1 N