Instruction Manual

67
E SR-750 UM
7-3 RS-232C Communication
This section describes the RS-232C communication of the SR-750 Series.
RS-232C Communication Configuration
Before using the RS-232C communication, set the communication conditions for
the SR-750 Series and the control device.
 SR-750 Series configuration
Use AutoID Network Navigator to configure the following:
• Communication conditions : Baud rate, data bit length, parity, and stop bit length
• Communication protocol : None, PASS/RTRY, or ACK/NAK
• Communication data format : Header and Terminator
Reference
Set the same settings for both the control device and the SR-750
Series.
 Default settings for RS-232C
The default settings for RS-232C are as follows.
• Baud rate : 115200 bps
• Data bit length : 8 bit
• Parity : Even
• Stop bit length : 1 bit
Reference
Press and hold the Test button for 6 seconds or longer to return the SR-
750 Series to the default configuration.
"3-1 Using the SR-750 Series (Page 9)"
Communication Protocol
RS-232C communication has 3 communication protocols available. Set it
according to the usage.
No Handshaking
The SR-750 Series sends read data to the control device without handshaking.
PASS/RTRY
The SR-750 Series sends read data to the control device using the following
protocol:
1 The SR-750 Series sends data to the control device.
2 The SR-750 Series waits for a response (PASS: Transmission
successful, RTRY: Request to resend) from the control device.
The SR-750 Series can still read codes while waiting for a response. Data read
while waiting for a response from the computer will be stored in the send buffer.
3 The host computer sends one of the following responses to the SR-
750 Series.
• PASS: Transmission complete. (The device does not respond to PASS)
• RTRY: Resend the same data to the control device and wait for a PASS
response.
Point
If the SR-750 Series send buffer is overloaded, "E4" is displayed
on the multi LED and reading operation is stopped.
• When "PASS" is received, "OVER" is sent to the control device
and an error occurs.
• When another "PASS" is received, the operation resumes.
Read data
Read data
Response
z PASS and RTRY formats
PASS (RTRY ) or PASS ( RTRY )
* at the beginning and at the end can be added.
Important
• The SR-750 Series is able to receive any command while waiting
for a response. This allows for a response to a command to be
sent without delay.
• If the SR-750 Series receives a RESET command while waiting
for a response, the send buffer will be cleared.
ACK/NAK
This protocol uses (0x06) instead of "PASS" and (0x15) instead of
"RTRY" in the PASS/RTRY protocol.
Other than the differences in the character strings to send, this protocol is identical
to the PASS/RTRY protocol.
Point
If the SR-750 Series' send buffer is overloaded, reading operation
will be stopped.
• When "ACK" is received, "OVER" is sent to the control device
and an error occurs.
• When another "ACK" is received, the operation resumes.
 ACK/NAK formats
Send [ACK] (0x06) and [NAK] (0x15) only, but do not append header nor
terminator.
Send Buffer Capacity
• The send buffer of the SR-750 Series can hold up to 10KB of data.
The number of characters for each entry saved in the send buffer includes the
header and terminator.
• When the number of characters in data exceeds 10KB, the send buffer overflows.
 Send Buffer Overflow
If the send buffer overflows, the SR-750 Series will send the following message
and an error occurs.
• "E" and "4" are displayed alternately on the multiple LED.
• ERR BUSY is output. (when OUT terminal is specified)
• When PASS/RTRY or ACK/NAK is set and PASS or ACK is received, "OVER" is
output.
To resume from buffer overflowed status, try the following operations:
• Send the buffer clear command "BCLR" from the control device.
• When PASS/RTRY or ACK/NAK is set, send PASS or ACK again
* Send buffer also can be cleared with a "RESET" command or cycling power.
* When a "BCLR" command is received while the send buffer is not overflowed,
data currently stored in the send buffer will be cleared.
CR
CR
STX
ETX
STX
ETX
ESC
LF
ACK
NAK