Siemens UL 489, UL1066 specifications What the Event Bytes Contain, COM16 slave Send Event

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What the Event Bytes Contain COM16 slave Receive Event

For a COM16 slave, an event byte returned by the Fetch Communications Event Log function can be either of two types. The type is defined by bit 7 (the high–order bit) in each byte.

The slave stores this type of event byte when a query message is received. It is stored before the slave processes the message. This event is defined by bit 7 set to a logic “1”. The other bits will be set to a logic “1” if the corresponding condition is TRUE. The bit layout is:

Bit Contents

0Not Used

1Communications Error

2Not Used

3Not Used

4Character Overrun

5Currently in Listen Only Mode (always zero, the COM16 does not support Listen Only Mode)

6Broadcast Received

7 1

Table 3-2

COM16 slave Send Event

The slave stores this type of event byte when it finishes processing a query message. It is stored if the slave returned a normal or exception response, or no response. This event is defined by bit 7 set to a logic “0”, with bit 6 set to a “1”. The other bits will be set to a logic “1” if the corresponding condition is TRUE.

The bit layout is:

Bit Contents

0Read Exception Sent (Exception Codes 1-3)

1Slave Abort Exception Sent (Exception Code 4)

2Slave Busy Exception Sent (Exception Codes 5-6)

3Slave Program NAK Exception Sent (Exception Code 7)

4Write Timeout Error Occurred

5Currently in Listen Only Mode (always zero, the COM16 does not support Listen Only Mode)

61

7 0

Table 3-3

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WL MODBUS Communication and Electronic Accessories • January 2005