KERNAL ENTRY:

OPEN ($FFC0) (See KERNAL specifications for more information on entry conditions and instructions.)

IMPORTANT NOTE: In a BASIC program, the RS-232 OPEN command should be performed before creating any variables or arrays because an automatic CLR is performed when an RS-232 channel is OPENed (This is due to the allocation of 512 bytes at the top of memory.) Also remember that your program will be destroyed if 512 bytes of space are not available at the time of the OPEN statement.

GETTING DATA FROM AN RS-232 CHANNEL

When getting data from an RS-232 channel, the Commodore 64 receiver buffer will hold up to 255 characters before the buffer overflows. This is indicated in the RS-232 status word (ST in BASIC, or RSSTAT in machine language). If an overflow occurs, then all characters received during a full buffer condition, from that point on, are lost. Obviously, it pays to keep the buffer as clear as possible.

If you wish to receive RS-232 data at high speeds (BASIC can only go so fast, especially considering garbage collects. This can cause the receiver buffer to overflow), you will have to use machine language routines to handle this type of data burst.

BASIC SYNTAX:
Recommended: GET#lfn, <string variable>
NOT Recommended: INPUT#lfn <variable list>

KERNAL ENTRIES:

• CHKIN ($FFC6)-See Memory Map for more information on entry and exit conditions.
• GETIN ($FFE4)-See Memory Map for more information on entry and exit conditions.
• CHRIN ($FFCF)-See Memory Map for more information on entry and exit conditions.