Perle Systems Iolan Sds4 Hl Device Server 4030370 User Manual

Utilities 421

API I/O Access Over TruePort

You can access IOLAN I/O data through TruePort using the Perle API. The API uses the 
command/response format. See the 

 sample program, found on the product CD-ROM, 

for an example implementation.

All data in the Request must be sent as a single write to the COM port. The API command takes the 
following format:

The API command takes the following response format:

1

Function Code (in hexadecimal):

z

01—Get read/write boolean register

z

03—Get read/write register

z

04—Get read only register

z

15—Set read/write boolean register (0x0F)

z

16—Set read/write register (0x10)

2

Starting register number (see 

for this value).

2

Number of registers to act on starting from the register defined in byte 
2 above.

n

Data for write. Some values must be read/written as a unit consisting of 

2 consecutive registers. If the request is to write, the data to write 

follows the number of registers. If accessing registers consisting of 2 
bytes or 4 bytes, the data is in big endian (network order) format.

1

Function code of request if no error. Most significant bit will be set if 
an error occurred.

1

Length of data in response if no error occurred. If an error occurred, the 

byte will contain the error code (see the 

 table below).

n

Data response for request (the number of bytes is dependent on the 

number and type of registers requested). If the request returns 2 or 4 
byte values, it will be in big endian (network order) format. If the 

request returns boolean values, the least significant bit (bit 0) represents 

the first value requested and bits 1 to 7 represents subsequent boolean 
values. If more than 8 boolean registers are requested, they are returned 

in successive bytes.