Rockwell-automation 1747-PCIS API Software - Open Controller Uživatelský manuál stáhnout pdf (Strana 50)

Publication 1747-UM002A-US-P - June 2000

3-18 Developing Applications

Determining Partition Sizes

for Shared Memory

The host application initializes the scanner by providing partitioning

information, which contains the size of memory to be reserved in the

shared memory for the input and output images. The size of memory

to be reserved for each of the images must be greater than or equal to

the number of input and output words required by each module. The

host application can’t communicate with the scanner until it has been

initialized.

The partitioning information is passed to OC_InitScanner in the

OCINIT structure, which is defined as:

typedef struct tagOCINIT {

WORD OutputImageSize; /* size in bytes */

WORD InputImageSize; /* size in bytes */

WORD HostRetentiveDataSize; /* size in bytes */

} OCINIT;

To determine the input and output image sizes, call

OC_CreateIOConfiguration with a configuration that contains the I/O

modules to be installed. OC_CreateIOConfiguration returns the

number of bytes of I/O required by each module. Or you can use

OC_GetIOConfig to use the current configuration, if one exists. The

input and output sizes are based on the number of words of I/O

required by each module. As an estimate, take the total number of

input and output words for all the modules in the system and multiply

by two to get the number of required bytes. The following code

fragment calculates the number of bytes required by the input and

output images:

OCINIT initinfo;

OCIOCFG iocfg;

int i,numslots;

/* assuming application has filled iocfg with I/O configuration */

OC_CreateIOConfiguration(&iocfg);

numslots = iocfg.Rack1Size + iocfg.Rack2Size + iocfg.Rack3Size;

if ( numslots > 31 ) numslots = 31;

initinfo.OutputImageSize = initinfo.InputImageSize = 0;

for ( i=1 ; i<numslots ; i++) {

initinfo.OutputImageSize += ((iocfg.SlotCfg[i].OutputSize+1) / 2) * 2;

initinfo.InputImageSize += ((iocfg.SlotCfg[i].InputSize+1) / 2) * 2;

}

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Rockwell-automation 1747-PCIS API Software - Open Controller Uživatelský manuál Strana 50