IAI America XSEL Ethernet - Manual (Page 25)

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4.4.1 Little Endian Operation
The default endian mode of DI/DO operation commands of the X-SEL controller is the little endian.
In the little endian mode, the remote I/O field accessed via word operation with an IN, INB, OUT or
OUTB command of the X-SEL controller will have its upper and lower bytes reversed in relation to
the X-SEL data if the same field is word-accessed via Modbus/TCP.
The following examples are based on 256-bit assignments from the head DO number (= 300) in
X-SEL as Modbus/TCP remote I/Os.
(Note) Remote I/Os can be defined only as consecutive numbers.
The assignable head number must satisfy: 300 + 8n (31
 n  0).
The total number of assignable bits must satisfy: m + n < 32 & 32
 m, where m represents
the number of assigned remote I/O bytes.
[Modbus/TCP input areas (assignment of X-SEL DO area 300 onward)]
Address
BIT7
(MSB)
6 5 4 3 2 1
0
(LSB)
X-SEL DO 307 306 305 304 303 302 301 300
Modbus/TCP bit address 0 1 2 3 4 5 6 7
Modbus/TCP word address 0 Lower byte
Modbus input status 10001 10002 10003 10004 10005 10006 10007 10008
Modbus input register 30001 Lower byte
X-SEL DO 315 314 313 314 315 310 309 308
Modbus/TCP bit address 8 9 10 11 12 13 14 15
Modbus/TCP word address 0 Upper byte
Modbus input status 10009 10010 10011 10012 10013 10014 10015 10016
Modbus input register 30001 Upper byte
:
:
X-SEL DO 547 546 545 544 543 542 541 540
Modbus/TCP bit address 240 241 242 243 244 245 246 247
Modbus/TCP word address 15 Lower byte
Modbus input status 10248 10249 10250 10251 10252 10253 10254 10255
Modbus input register 30016 Lower byte
X-SEL DO 555 554 553 552 551 550 549 548
Modbus/TCP bit address 15 Upper byte
Modbus/TCP word address 248 249 250 251 252 253 254 255
Modbus input status 10249 10250 10251 10252 10253 10254 10255 10256
Modbus input register 30016 Upper byte
Cannot be used
Input status: input discretes single bit, provided by an I/O system, read-only
Output coil: output discretes single bit, alterable by an application program, read-write
Input register: input registers 16-bit quantity, provided by an I/O system, read-only
Output register: output registers 16-bit quantity, alterable by an application program, read-write
The output areas are described on the next page.