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Appendix A
Operating Precautions
Changing from C200H-ASC02
Execution Time
The time required by the C200H-ASC11/ASC12/ASC31 to execute commands is different from the C200H-
ASC02. Therefore, the execution time of BASIC programs will depend on the ASCII Unit being used.
Machine Language Programs
Programs created on the C200H-ASC02 using machine language cannot be used with the C200H-ASC11,
C200H-ASC21, or C200H-ASC31 ASCII Unit.
Integer Format
In the C200H-ASC11/ASC21/ASC31, real numbers (single-precision and double-precision) are in floating-point
constant format. Since the standard has changed to conform to IEEE-754, the results of operations using real
numbers may change. If precise operations are required, use double-precision variables for the arguments.
Example:
10 A# = 0.9 + 0.1
20 A = ACOS (A#)
Command Competition in Interrupt Processing
In the C200H-ASC02, an interrupt cannot be generated while a BASIC program command is being executed.
This is possible, however, for the C200H-ASC11/ASC21/ASC31. Therefore, if an interrupt is generated while a
command is being executed and the same command is included in the interrupt subroutine, there will be com-
petition between the two commands and operations will not run smoothly (e.g., if an interrupt is generated
while the PRINT command is executing and the interrupt subroutine contains the PRINT, INPUT, LINE INPUT
command for the same port). To stop competition between commands from occurring, exclusively control inter-
rupts by using control commands to enable, disable, and stop execution.
Handling Communications Errors
In the C200H-ASC02, the BASIC program will not stop executing due to a communications error. In the same
way, if a communications error is generated with the C200H-ASC11/ASC21/ASC31 and the ON ERROR com-
mand is not used, the BASIC program will not stop executing. The BASIC program will stop executing, how-
ever, if the ON ERROR command is used and a new error (not a communications error) is generated while an
error interrupt subroutine is being executed.
Internal Bit Allocations
The functions of the words and bits allocated in memory have changed. Make sure to check the allocations
when using ladder programs in the CPU Unit. Functions and operations for the ASCII Busy Flag have changed,
so exercise caution when using this flag.
ASCII Unit System Setup
The method of setting up the ASCII Unit system has changed from using the DIP switch on the back of the Unit
to using 10 words at the beginning of the DM Allocation Area. Use a PC peripheral device to set the allocated
DM words in the CPU Unit.
Summary of Contents for C200H-ASC11
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