Omega Speaker Systems VR200 - Manual (Page 10)

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1 INST
ALLING THE RS-422-A
INTERF
ACE
Note
The VR200 identifies an LF as the end of a text when receiving data (and sends a CR and LF as the terminator when sending
data). As shown in the example in Figure 1.6, when a CR and LF are used as the terminator, the CR is ignored. Take care when
communicating with a PC, since some PCs may not send the LF character depending on the mode when the PRINT command,
etc. is invoked.
1.4.3 Input Buffer
The input buffer of the VR200 recorder is a rotary buffer. The rotary buffer outputs a
text on a first-in, first-out basis while storing the data in turn. The user must be aware
of this when programming, and take care to prevent the buffer from overflowing. One
merit of the rotary buffer is that it can flexibly cope with more than one text being sent
contiguously because of the low loss in case of variable text length.
Text 1
Te
xt
2
T
e
x
t
3
Start 1
Start 2
Start 3
End 1
End 2
End 3
Figure 1.7 Rotary Buffer
1.4.4 Buffer Overflow
As described already, the input buffer is necessary for data communication. The
capacity, however, is limited (256 bytes for a 4-channel model). Thus, in the receiver,
the buffer capacity may not be sufficient if a lot of data is sent in a short time, causing
some data to be dropped and adversely affecting the data communications (buffer
overflow).
To prevent buffer overflow, confirm the status of the VR200 using the ESC S command
immediately after a command has been sent (from the PC).
Note
A PC may not be able to send the ESC S command after having sent the LF or FM command.
After receiving the ESC S command, the VR200 outputs its status to the PC. This is
done in the following sequence. The VR200 first stores the ESC S command in the
input buffer, then this command is read from the buffer. Consequently, the VR200
outputs its status to the PC. If the PC does not send the next command until it receives
the VR200 status, the next command will be always received without fail, since there
must be a space in the input buffer of the VR200.
1.4 Data Configuration