Honeywell XYR 5000 LINE manual Modbus Commands, Command 03-Read Holding Registers

device ID. The Base Radio uses register addresses 1 through 10 with each subsequent group of 10 registers used by a Transmitter.

The RF online/offline status of a Transmitter can be determined through a number of different sources. In the Base Radio holding registers, a count of the current number of online Transmitters can be found at address 00004. Also the individual online/offline status of each Transmitter is stored in the Base Radio holding registers at addresses 00005, 00006, 00007, and 00008. These registers are bit field variables with each bit of the 16-bit number representing the status of a Transmitter. If the bit is set, the corresponding Transmitter is online. If the bit is cleared, the corresponding Transmitter is offline.

In the Transmitter holding registers, bit 1 in the Transmitter & Sensor Status holding register holds the online/offline status of the particular device. Any Transmitter that is currently offline will return NaN (Not a Number) when queried for its primary or secondary measurement value. Note that if a Transmitter is online and is a single measurement device type, NaN will also be returned for the Secondary Sensor Value, as the measurement does not exist in these devices.

6.3Modbus Commands

The Base Radio responds to six Modbus commands including the Read Holding Registers (03), Diagnostic (08), Get Com Event Count (11), Get Com Event Log (12), Report Slave ID (17), and Read Device Identification (43). The Read Holding Registers command provides the bulk of the functionality with the remaining commands being used for diagnostics/troubleshooting purposes. No other Modbus commands are supported and will be responded to with an ILLEGAL FUNCTION exception (code 01). A description of each command code is listed in the following sections.

6.3.1 Command 03-Read Holding Registers

This command is used to read the contents of a contiguous block of holding registers in a Base Radio or Transmitter. If an invalid register address is requested, an ILLEGAL DATA ADDRESS exception (code 02) will be returned.

Section 6.4 lists the holding registers for the Base Radio and Transmitters, as well as how to understand the contents of the registers.

6.3.2 Command 08- Diagnostic

This command provides a number of tests for checking the communications between the Base Radio and the Host master device.

Subfunction Code	Transmitter Device Status
0	Return Query Data
1	Restart Communications Option
2	Return Diagnostics Register
3	Change ASC-II Input Delimiter (NOT SUPPORTED)
4	Force Listen Only Mode
5-9	NOT USED
10	Clear Counters & Diagnostics Register
11	Return Bus Message Count

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