Page 391 - Programming Microcontrollers in C

376 Chapter 7 Advanced Topics

break;
case ‘r’: /* reset the system */
reset(&epro);
break;
}
}
}
Listing 7-12: Monitor Program

The SAVEIT() Routine

The saveit() function receives the data entered from the
keyboard in monitor(), encodes these data and saves the result in
EEPROM for later use. This program is set up to save the data in a
linked list. The linked list is an array DLEN, found in phone.h, long
and each member of the list is of the type Entry. These data are
stored in the main data array and access to these data is made through
the values stored in the corresponding Entry for each set of data.
In the header file phone.h, several macros are defined that make it
somewhat easier to code this function. The first three entries in the data
array are used for special purposes. Therefore, these values are renamed
as macros to make the code more understandable. These macros are:
#define NEXT_OPEN epro->data[0]
#define START_OF_LIST epro->data[1]
#define LIST_ENTRIES epro->data[2]

Useful names can now be used rather than the cryptic actual names
of these various memory locations.
On entry to this function, both the name and number parameters
are encoded and the result is saved in the array name[] and
number[] respectively. The next block of code determines if there
is enough room in the EEPROM array to store all of the data. In the
event that there is not enough room, the message “*** buffer
full***” is sent to the output and control is returned to the monitor
program when return is executed.
/************************************************
This program works in conjunction with moni­
tor(). It receives the input found in monitor