Measurement Computing Personal488 rev.3.0 For DOS & Windows 3.Xi - Manual (Page 77)

8E. Microsoft C II. SOFTWARE GUIDES - 8. Driver488/DRV
II-62 Personal488 User’s Manual, Rev. 3.0
receive buffer, chars . This means chars must be an array of known size, for example,
char chars[256] , not char*chars .
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IEEEPRTF and IEEESCNF are IEEE 488 versions of PRINTF and SCANF , respectively.
int ieeeprtf(format,...)
char *format
int ieeescnf(format,a,b,c,d,e)
char *format,*a,*b,*c,*d,*e
The IEEEPRTF accepts a format string and a list of arguments. It formats its arguments according
to the specified format and sends the formatted string to Driver488/DRV. The IEEESCNF accepts
a format string and up to 5 pointers (to the types specified in the format string). It reads a string of
up to 256 bytes from Driver488/DRV, terminates it with a zero, converts it according to the format
string, and places the converted values into the variables pointed to by the specified pointers.
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RAWMODE sets the file specified by handle for “raw mode” I/O.
int rawmode(handle)
int handle
In “raw mode” MS-DOS does not interpret the characters received from the file. In particular,
control-Z is not taken as end-of-file. “Raw mode” is usually appropriate for IEEE 488
communications because it does not interfere with the transfer of binary data and because it is
much more efficient than “non-raw mode” I/O.
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IEEEINIT establishes communications with Driver488/DRV and configures it for use with C.
int ieeeinit()
It first opens the file IEEE for both reading and writing and puts the file descriptor into IEEE . It
then puts the file into “raw mode”. Driver488/DRV is then initialized by sending the IOCTL
“BREAK” and RESET commands. Normal output from C is terminated by a new-line (line feed)
character, and returned strings should be terminated by a null, so EOL OUT LF and EOL IN $0
commands are then issued. Finally a FILL ERROR command is issued to enable SEQUENCE - NO
DATA AVAILABLE error detection. If an error is detected during any of these commands,
IEEEINIT returns a -1 , otherwise it returns a zero ( 0 ).
CRITERR.ASM (Microsoft C & Turbo C)
Normally, when Driver488/DRV detects an error, perhaps due to a syntax error in a command, it
responds with an I/O error to DOS. When this happens, DOS normally issues an
ABORT , RETRY or
IGNORE message and waits for a response from the keyboard. There is no way for the user’s program
to detect such an error, determine the cause, and take appropriate action. However, DOS does provide
a method of redefining the action to be taken on such a “critical error”.
CRITERR.ASM contains a
critical error handler that, when invoked, makes it appear to the calling program that some less-critical
error has occurred. The critical error handler is installed by
CRIT_ON() and removed by
CRIT_OFF() .The critical error handler is also automatically removed by DOS when the program exits.
The following program fragment demonstrates the use of the critical error handler:
#include “criterr.h”
crit_on(ieee);
if (ieeewt(“output 16;F0X”) == -1) {
printf(“Error writing F0X to device 16, \n”);
crit_off();
ioctl_wt(ieee,"break",5);
ieeewt(“eol out lf\r\n”);
ieeewt(“status\n”);
ieeerd(response);
printf(“status = %s\n”,response);
crit_on(ieee);
}
We must first #include the header file with the definitions of the critical error routines. We then
enable critical error trapping with CRIT_ON which takes as a parameter the handle of the file for which