scx_setbrdparm( )

Description | Cautions | Example | Errors | See Also

Name:	int scx_setbrdparm (devh, param, valuep)
Inputs:	int devh	SCX160 SCxbus Adapter device handle
	unsigned char param	parameter name
	void *valuep	pointer to the location of the parameter value
Returns:	0 on success -1 on failure
Includes:	scxlib.h
Category:	Configuration
Mode:	synchronous

Description

The scx_setbrdparm( ) function changes board level parameters.

Parameter	Description
devh:	Specifies the SCX160 SCxbus Adapter device handle.
param:	Specifies the name of the parameter, see Table 13.  SCX160 User Selectable Parameters, below for parameter defines and their description.
valuep:	Points to the location of the parameter value.

The SCXBP_FIFO_ERR_THRESH parameter specifies the FIFO buffer error threshold. Most FIFO errors occur due to clock reference drift, maintenance activities on the network and any other activity that impacts the clock reference signal. Therefore, error rates will vary depending on the environment in which the SCX160 SCxbus Adapter system operates. Each user must determine an acceptable error threshold for their system. A typical rate of 255 slips in a 24 hour period (error threshold setting of 11 slips/hour) would not be uncommon.

The SCXBP_DRIVER_ERR_THRESH parameter specifies the SCX160 bus driver error threshold. Driver errors reflect impairments due to transmission line inefficiency, bus contention, excessive cable length, improper SCSI-3 termination and similar phenomena. Typically, copper-based transmission lines can be expected to offer a Bit Error Rate (BER) of better than 1 x 10-6 (1 error per 1 million bits). Each user must determine an acceptable BER threshold for their system while keeping in mind that each data stream runs at 4.096 M bits/sec. A threshold of 14,000 errors/hour (less than 1 error per million bits) may be appropriate for a network with moderate to heavy traffic between nodes.

Table 13.  SCX160 User Selectable Parameters

Define	B	Default	R/W	Description
SCXBP_SCX_CLOCK_MODE	1	Default SCxbus clocking configured at download time.	R/W	Specifies clocking for the SCxbus interface of the SCX160 SCxbus Adapter. The SCxbus interface can be set to any of the following:   SCXCM_MASTER - provides right SCxbus clock   SCXCM_SLAVE - receives clock from another SCxbus device   SCXCM_FALLBACK_MASTER - receives right clock from another SCxbus device, and generates left SCxbus clock to be used by other SCxbus devices if the right SCxbus clock is unavailable
SCXBP_CLOCK_REF	1	Default SCX160 Clock Reference Signal configured at download time.	R/W	Specifies source of the SCX160 SCxbus Adapter clock reference signal. The clock source can be any one of the following:   SCXCS_INTERNAL - use Internal Clock   SCXCS_SCBUS - derive clock from SCbus   SCXCS_SCXBUS_RIGHT - derive clock from SCxbus Right Clock   SCXCS_SCXBUS_LEFT - derive clock from SCxbus Left Clock   SCXCS_EXTERNAL - use External 8 kHz Clock
SCXBP_FIFO_ERR_THRESH	4	0xFFFFFFFF	R/W	Specifies FIFO buffer error threshold that must be exceeded before an alarm is generated:   Lower word is Over Flow/Under Flow (Slip) Threshold (Valid Range:0 _ Thresh _ 0xFFFF)   Upper word is Frame Error Threshold (Valid Range:0 _ Thresh _ 0xFFFF)
SCXBP_DRIVER_ERR_THRESH	4	0xFFFFFFFF	R/W	Specifies SCX160 driver error threshold that must be exceeded before an alarm is generated.   Lower word is SCbus Threshold (Valid Range:0 _ Thresh _ 0xFFFF)   Upper word is SCxbus Threshold (Valid Range:0 _ Thresh _ 0xFFFF)
SCXBP_SC_CLOCK_MODE	1	Default SCbus clocking configured at download time.	R/W	Specifies clocking for SCbus interface of the SCX160 SCxbus Adapter. The SCbus interface can be set to any of the following:   SCXCM_MASTER - provides SCbus clock   SCXCM_SLAVE - receives clock from another SCbus device   SCXCM_FALLBACK_MASTER - receives clock from another SCbus device, however, is ready to provide master SCbus clock if the master clock fails.
Legend:	B (2nd) column lists the length in Byte(s); R/W column: R = Read; W = Write

Cautions

This function will fail if an invalid device handle is specified.

Example

#include <windows.h>  
#include <stdio.h>  
#include <stdlib.h>  
#include <errno.h>  
#include <srllib.h>  
#include <scxlib.h>  
   
int      devh;                                 /* SCX160 device handle */  
unsigned   char   parm_val = SCXCM_MASTER;     /* Parameter Value      */  
   
/* Open SCX160 board */  
if ((devh = scx_open("scxB1", 0)) == -1) {  
      printf("Cannot open board scxB1.  errno = %d \n", errno);  
      exit(1);  
}  
   
/* Set SCxbus clock mode to Master */  
if (scx_setbrdparm(devh, SCXBP_SCX_CLOCK_MODE, &parm_val) == -1) {  
      printf("ERROR: scx_setbrdparm( ) failed, %s \n", ATDV_ERRMSGP(devh));  
      exit(1);  
}  
   
/* Close the SCX160 Board */  
scx_close(devh);

Errors

If the function returns -1, use the SRL Standard Attribute function ATDV_LASTERR( ) to obtain the error code, or you can use the ATDV_ERRMSGP( ) function to obtain a descriptive error message. The error codes returned by ATDV_LASTERR( ) function are listed in Chapter 7.  Errors.

See Also

• scx_getbrdparm( )

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