Measurement Computing Personal488 rev.3.0 For DOS & Windows 3.Xi - Manual (Page 95)

8H. Turbo C II. SOFTWARE GUIDES - 8. Driver488/DRV
II-80 Personal488 User’s Manual, Rev. 3.0
int cklpint(void)
int _false_(void)
int (*ieee_cki)(void) = _false_
void no_op(void)
void (*ieee_isr)(void) = no_op
Driver488/DRV signals interrupts, which are enabled with the ARM command, by causing the light
pen signal to appear “true.” The CKLPINT checks that Driver488/DRV is able to service an
interrupt (the response from IOCTL_RD is 0 ) and then checks if an interrupt is pending by
checking the light pen status. The IEEEWT routine (described below) calls the function pointed to
by IEEE_CKI to determine if an IEEE interrupt needs to be serviced. The IEEE_CKI normally
points to the function _false_ which always returns zero ( 0 ). To enable interrupt checking
IEEE_CKI must be redirected to point to CKLPINT . Interrupt checking is disabled by pointing
IEEE_CKI back to _false_ . Once an interrupt has been detected, IEEEWT calls the interrupt
service routine pointed to by IEEE_ISR to service the interrupt. The IEEE_ISR initially points to
no_op , a function that does nothing, but it may be redirected as needed to specify the appropriate
interrupt service routine for each part of a program.
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_IEEEWT and _IEEERD are very similar to the unbuffered _ WRITE and _ READ routines provided
in the C library.
int _ieeewt(int handle,char chars[])
int _ieeerd(int handle,char chars[],int size)
#define ieeewt(chars) _ieeewt(ieee,chars)
#define ieeerd(chars) _ieeerd(ieee,chars,sizeof(chars))
The _IEEEWT differs from _ WRITE in that it checks for Driver488/DRV interrupts before writing,
determines the number of characters to write by using STRLEN , and prints an error message if an
error has occurred during writing. The _IEEERD differs from _ READ only in that it prints an error
message if an error has occurred during reading. IEEEWT and IEEERD (without the leading
underscore) write and read to the file IEEE . Notice that IEEERD uses SIZEOF to determine the
number of characters to read. This only works if SIZEOF can determine the number of bytes in the
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(char *format, ...)
int ieeescnf(char *format, ...)
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 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(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(void);
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 ).