BFILL

BFILL
Description	Byte fill
Format	BFILL
Code	140 1308
Affected	P,X,T, memory region defined by X,T
Type	User
Architecture	ND-100, ND-110

BFILL is an assembly instruction. A byte operand memory area defined by the X and T registers is filled with the value of the right-most byte in the A register.

The P register is incremented by two when this instruction is finished, i.e. any instruction directly following BFILL will not be executed.

The A, X and T registers should be set to appropriate values before execution of BFILL. The X and T registers will also be modified by the instruction.

Before execution

A: Bit 0-7:  The value to fill into each byte of the destination field.
X: Bit 0-15: The destination field's word address in memory.
T: Bit 15:   This bit specifies whether the byte operand starts 
             in the left byte or right byte of the address defined by X.
             Bit 15 = 0, left byte
             Bit 15 = 1, right byte
   Bit 14:   Page table mode: Bit 14 = 1 selects the alternative page table.
   Bit 13:   This bit should be 0.
   Bit 12:   Not used.
   Bit 11-0: Field length in number of bytes (0-4095).

After execution

X: Bit 0-15: The word address of the byte following the last byte.
T: Bit 15:   This bit specifies whether the byte following the last byte is
             in the left byte or right byte of the address defined by X.
   Bit 11-0: Set to zero.

Example 1

Memory area before execution, each address holds 2 bytes (1 word):
Address: 0  0 0
         1  0 0
         2  0 0
         3  0 0
A register = 1
X register = 1
T register = 0x0003 (bit 15 = 0, length field = 3)

Memory area after execution:
Address: 0  0 0
         1  1 1
         2  1 0
         3  0 0
X register = 2
T register = 0x8000 (bit 15 = 1)
P:= P+2

Example 2

Memory area before execution, each address holds 2 bytes (1 word), work on alternative page table:
Address: 0  0 0
         1  0 0
         2  0 0
         3  0 0
A register = 1
X register = 1
T register = 0xC003 (bit 15 = 1 (right byte), bit 14 = 1 (use APT), length field = 3)

Memory area after execution:
Address: 0  0 0
         1  0 1
         2  1 1
         3  0 0
X register = 3
T register = 0x4000 (bit 15 = 0)
P:= P+2

References

• Norsk Data Document ND–06.014.02 ND-100 REFERENCE MANUAL Pages 3-27,3-28
• Norsk Data Document ND–06.029.01 ND-110 Instruction Set Pages 92-93

The older document is more accurate for this instruction.