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Negative Flag, N SR bit 25402 turns ON when the result of a calculation is negative.
Overflow Flag, OF SR bit 25404 turns ON when the result of a binary addition or subtraction ex-
ceeds 7FFF or 7FFFFFFF.
Underflow Flag, UF SR bit 25405 turns ON when the result of a signed binary addition or subtraction
exceeds 8000 or 80000000.
Carry Flag, CY SR bit 25504 turns ON when there is a carry in the result of an arithmetic opera-
tion or when a rotate or shift instruction moves a “1” into CY. The content of CY is
also used in some arithmetic operations, e.g., it is added or subtracted along
with other operands. This flag can be set and cleared from the program using the
Set Carry and Clear Carry instructions.
Greater Than Flag, GR SR bit 25505 turns ON when the result of a comparison shows the first of two
operands to be greater than the second.
Equal Flag, EQ SR bit 25506 turns ON when the result of a comparison shows two operands to
be equal or when the result of an arithmetic operation is zero.
Less Than Flag, LE SR bit 25507 turns ON when the result of a comparison shows the first of two
operands to be less than the second.
Note The four arithmetic flags are turned OFF when END(01) is executed.
3-4-18 Interrupt Subroutine Areas
The following areas are used in subroutine interrupt processing.
SR bits 26200 to 26215 are used to set the maximum processing time of the in-
terrupt subroutine. Processing times are determined to within 0.1 ms incre-
ments.
SR bits 26300 to 26315 contain the maximum processing time interrupt subrou-
tine number. Bit 15 will be ON if there is an interruption.
3-4-19 RS-232C Port Communications Areas
RS-232C Port Error Code SR bits 26400 to 26403 set when there is a RS-232C port error.
Error code Error type Error conditions Valid modes
0 No error --- All modes
1 Parity error When data received differs from
positive/negative parity setting.
All modes
2 Framing error When step bit cannot be detected. All modes
3 Overrun error When data is not properly received. All modes
4 Timeout error When a timeout occurs for two PCs linked
one-to-one.
1:1 PC Link slave or 1:1
PC Link master
SR bit 26404 turns ON when there is a RS-232C port communication error.
SR bit 26405 turns ON when the PC is ready to transmit data.
SR bit 26406 turns ON when the PC has completed reading data from a
RS-232C device.
SR bit 26407 turns ON when data overflow occurs following the reception of
data.
SR 26500 to SR 26515 contains the number of RS-232C port receptions in Gen-
eral I/O Mode.
Interrupt Subroutine
Maximum Processing Time
Area
Maximum Processing Time
Interrupt Subroutine
Number Area
RS-232C Port
Communication Error Bit
RS-232C Port Send Ready
Flag
RS-232C Port Reception
Completed Flag
RS-232C Port Reception
Overflow Flag
RS-232C Reception Counter
SR (Special Relay) Area Section 3-4