Updated: 11 December 1998

VAX MACRO and Instruction Set Reference Manual

Divide Packed

Format

opcode divrlen.rw, divraddr.ab, divdlen.rw,

divdaddr.ab, quolen.rw, quoaddr.ab

Condition Codes

Exceptions

• reserved operand
• decimal overflow
• divide by zero

Opcodes

Description

The dividend string specified by the dividend length and dividend address operands is divided by the divisor string specified by the divisor length and divisor address operands. The quotient string specified by the quotient length and quotient address operands is replaced by the result.

Notes

1. This instruction allocates a 16-byte workspace on the stack. After execution, the stack pointer (SP) is restored to its original contents, and the contents of {(SP)--16}:{(SP)--1} are UNPREDICTABLE.
2. The division is performed, resulting in the following conditions:
   • The absolute value of the remainder (which is lost) is less than the absolute value of the divisor
   • The product of the absolute value of the quotient times the absolute value of the divisor is less than or equal to the absolute value of the dividend
   • The sign of the quotient is determined by the rules of algebra from the signs of the dividend and the divisor; if the value of the quotient is zero, the sign is always positive
3. After execution:

   R0 =	0
   R1 =	Address of the byte containing the most significant digit of the divisor string
   R2 =	0
   R3 =	Address of the byte containing the most significant digit of the dividend string
   R4 =	0
   R5 =	Address of the byte containing the most significant digit of the quotient string

4. The quotient string, R0 to R5, and the condition codes are UNPREDICTABLE if: the quotient string overlaps the divisor or dividend strings; the divisor or dividend string contains an invalid nibble; the divisor is zero; or a reserved operand abort occurs.

Move Packed

Format

opcode len.rw, srcaddr.ab, dstaddr.ab

Condition Codes

Exceptions

• reserved operand

Opcodes

Description

The destination string specified by the length and destination address operands is replaced by the source string specified by the length and source address operands.

Notes

1. After execution:

   R0 =	0
   R1 =	Address of the byte containing the most significant digit of the source string
   R2 =	0
   R3 =	Address of the byte containing the most significant digit of the destination string

2. The destination string, R0 to R3, and the condition codes are UNPREDICTABLE if: the destination string overlaps the source string; the source string contains an invalid nibble; or a reserved operand abort occurs.
3. If the source is --0, the result is +0, N is cleared, and Z is set.

Multiply Packed

Format

opcode mulrlen.rw, mulraddr.ab, muldlen.rw,

muldaddr.ab, prodlen.rw, prodaddr.ab

Condition Codes

Exceptions

• reserved operand
• decimal overflow

Opcodes

Description

The multiplicand string specified by the multiplicand length and multiplicand address operands is multiplied by the multiplier string specified by the multiplier length and multiplier address operands. The product string specified by the product length and product address operands is replaced by the result.

Notes

1. After execution:

   R0 =	0
   R1 =	Address of the byte containing the most significant digit of the multiplier string
   R2 =	0
   R3 =	Address of the byte containing the most significant digit of the multiplicand string
   R4 =	0
   R5 =	Address of the byte containing the most significant digit of the product string

2. The product string, R0 to R5, and the condition codes are UNPREDICTABLE if: the product string overlaps the multiplier or multiplicand strings; the multiplier or multiplicand strings contain an invalid nibble; or a reserved operand abort occurs.

Subtract Packed

Format

4operand: opcode sublen.rw, subaddr.ab,

diflen.rw, difaddr.ab

6operand: opcode sublen.rw, subaddr.ab,

minlen.rw, minaddr.ab,
diflen.rw, difaddr.ab

Condition Codes

Exceptions

• reserved operand
• decimal overflow

Opcodes

Description

In 4 operand format, the subtrahend string specified by the subtrahend length and subtrahend address operands is subtracted from the difference string specified by the difference length and difference address operands, and the difference string is replaced by the result.

In 6 operand format, the subtrahend string specified by the subtrahend length and subtrahend address operands is subtracted from the minuend string specified by the minuend length and minuend address operands. The difference string specified by the difference length and difference address operands is replaced by the result.

Notes

1. After execution of SUBP4:

   R0 =	0
   R1 =	Address of the byte containing the most significant digit of the subtrahend string
   R2 =	0
   R3 =	Address of the byte containing the most significant digit of the difference string

2. After execution of SUBP6:

   R0 =	0
   R1 =	Address of the byte containing the most significant digit of the subtrahend string
   R2 =	0
   R3 =	Address of the byte containing the most significant digit of the minuend string
   R4 =	0
   R5 =	Address of the byte containing the most significant digit of the difference string

3. The difference string, R0 to R3 (R0 to R5 for SUBP6), and the condition codes are UNPREDICTABLE if: the difference string overlaps the subtrahend or minuend strings; the subtrahend, minuend, or difference (4 operand only) strings contain an invalid nibble; or a reserved operand abort occurs.

9.2.12 The EDITPC Instruction and Its Pattern Operators

The operands to the EDITPC instruction are as follows:

1. A packed decimal string descriptor (as input). This is a standard VAX operand pair consisting of the length of the decimal string in digits (up to 31) and the starting address of the string.
2. A pattern specification, consisting of the starting address of a pattern operation editing sequence. VAX MACRO interprets a pattern specification in the same way as it interprets normal instructions.
3. The starting address of the output string. The output string is described by its starting address only, because the pattern defines the length unambiguously.

The EDITPC instruction manipulates two character registers and the four condition codes:

The fill register (R2<7:0>) contains the fill character. This is normally an ASCII blank but could be changed to an asterisk (*), for instance, for check protection.

The sign register (R2<15:8>) contains the sign character. Initially this register contains either an ASCII blank or a minus sign (--), depending upon the sign of the input. You can change the contents of this register to allow other sign representations such as plus/minus or plus/blank. You can also manipulate it to output special notations such as CR or DB. To implement a floating currency sign, you can change the sign register to the currency sign.

After execution, the condition codes describe the following:

N	The sign of the input
Z	The presence of a zero source
V	An overflow condition
C	The presence of significant digits

Condition code N is determined at the start of the instruction and remains unchanged (except for correcting a --0 input). The processor computes and updates the other condition codes as the instruction proceeds.

When the EDITPC instruction completes processing, registers R0 to R5 contain the values they would normally have after a decimal instruction.

Edit Packed to Character String

Format

opcode srclen.rw, srcaddr.ab, pattern.ab, dstaddr.ab

Condition Codes

Exceptions

• reserved operand
• decimal overflow

Opcodes

Description

The destination string specified by the pattern and destination address operands is replaced by the edited version of the source string specified by the source length and source address operands. The editing is performed according to the pattern string, starting at the address of the pattern operand and extending until a pattern end pattern operator (EO$END) is encountered.

The pattern string consists of 1-byte pattern operators. Some pattern operators take no operands. Some take a repeat count that is contained in the rightmost nibble of the pattern operator itself. The rest take a 1-byte operand that immediately follows the pattern operator. This operand is either an unsigned integer length or a byte character.

Table 9-1 lists the pattern operators that can be used with the EDITPC instruction to form a pattern. Subsequent pages define each pattern operator in a format similar to that of the normal instruction descriptions. In each case, if there is an operand, it is either a repeat count (r) from 1 to 15, an unsigned byte length (len), or a character byte (ch). The encoding of the pattern operators is represented graphically in Table 9-2.

See Appendix E for information about exceptions that affect the EDITPC instruction.

Notes

1. A reserved operand abort occurs if srclen GTRU 31.
2. The destination string is UNPREDICTABLE if any of the following is true:
   • The source string contains an invalid nibble.
   • The EO$ADJUST_INPUT operand is outside the range 1 to 31.
   • The source and destination strings overlap.
   • The pattern and destination strings overlap.
3. After execution, the following general registers have contents as specified:

   R0 =	Length of source string
   R1 =	Address of the byte containing the most significant digit of the source string
   R2 =	0
   R3 =	Address of the byte containing the EO$END pattern operator
   R4 =	0
   R5 =	Address of 1 byte beyond the last byte of the destination string

   
   If the destination string is UNPREDICTABLE, R0 to R5 and the condition codes are UNPREDICTABLE.
4. If V is set at the end and DV is enabled, a numeric overflow trap occurs unless the conditions in note 9 are satisfied.
5. The destination length is specified exactly by the pattern operators in the pattern string. If the pattern is incorrectly formed or if it is modified during the execution of the instruction, the length of the destination string is UNPREDICTABLE.
6. If the source is --0, the result may be --0 unless a fixup pattern operator is included (EO$BLANK_ZERO or EO$REPLACE_SIGN).
7. The contents of the destination string and the memory preceding it are UNPREDICTABLE if the length covered by EO$BLANK_ZERO or EO$REPLACE_SIGN is zero, or if it is outside the destination string.
8. If more input digits are requested by the pattern than are specified, a reserved operand abort is taken with R0 = --1 and R3 = location of the pattern operator that requested the extra digit. The condition codes and other registers are as specified in note 11. This abort cannot be continued.
9. If fewer input digits are requested by the pattern than are specified, a reserved operand abort is taken with R3 = location of EO$END pattern operator. The condition codes and other registers are as specified in note 11. This abort cannot be continued.
10. On an unimplemented or reserved pattern operator, a reserved operand fault is taken with R3 = location of the faulting pattern operator. The condition codes and other registers are as specified in note 11. This fault can be continued as long as the defined register state is manipulated according to the pattern operator description and the state specified as "implementation dependent" is preserved.

11. On a reserved operand exception, as specified in notes 8 to 10, FPD is set and the condition codes and registers are as follows:

    N =	{ src has minus sign}
    Z =	All source digits zero so far
    V =	Nonzero digits lost
    C =	Significance
    R0<31:16> =	--(count of source zeros to supply)
    R0<15:0> =	Remaining srclen
    R1 =	Current source location
    R2<31:16> =	Implementation dependent
    R2<15:8> =	Current contents of sign register
    R2<7:0> =	Current contents of fill register
    R3 =	Location of edit pattern operator causing exception
    R4 =	Implementation dependent
    R5 =	Location of next destination byte

Table 9-1 Summary of EDITPC Pattern Operators

Name	Operand	Summary
Insert operators
EO$INSERT	ch	Insert character, fill if insignificant
EO$STORE_SIGN	---	Insert sign
EO$FILL	r	Insert fill
Move operators
EO$MOVE	r	Move digits, fill if insignificant
EO$FLOAT	r	Move digits, floating sign
EO$END_FLOAT	---	End floating sign
Fixup operators
EO$BLANK_ZERO	len	Fill backward when 0
EO$REPLACE_SIGN	len	Replace with fill if --0
Load operators
EO$LOAD_FILL	ch	Load fill character
EO$LOAD_SIGN	ch	Load sign character
EO$LOAD_PLUS	ch	Load sign character if positive
EO$LOAD_MINUS	ch	Load sign character if negative
Control operators
EO$SET_SIGNIF	---	Set significance flag
EO$CLEAR_SIGNIF	---	Clear significance flag
EO$ADJUST_INPUT	len	Adjust source length
EO$END	---	End edit

• ch---One character
• r---Repeat count in the range 1 to 15
• len---Length in the range 1 to 255

Table 9-2 EDITPC Pattern Operator Encoding

Hex	Symbol	Notes
00	EO$END	---
01	EO$END_FLOAT	---
02	EO$CLEAR_SIGNIF	---
03	EO$SET_SIGNIF	---
04	EO$STORE_SIGN	---
05...1F	---	Reserved to Digital
20...3F	---	Reserved for all time
40	EO$LOAD_FILL	Character is in next byte
41	EO$LOAD_SIGN	Character is in next byte
42	EO$LOAD_PLUS	Character is in next byte
43	EO$LOAD_MINUS	Character is in next byte
44	EO$INSERT	Character is in next byte
45	EO$BLANK_ZERO	Unsigned length is in next byte
46	EO$REPLACE_SIGN	Unsigned length is in next byte
47	EO$ADJUST_INPUT	Unsigned length is in next byte
48...5F	---	Reserved to Digital
60...7F	---	Reserved to CSS and customers
80,90,A0	---	Reserved to Digital
81...8F	EO$FILL	---
91...9F	EO$MOVE	Repeat count is <3:0>
A1...AF	EO$FLOAT	---
B0...FE	---	Reserved to Digital
FF	---	Reserved for all time

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