at94k40al ATMEL Corporation, at94k40al Datasheet - Page 117

• Manufacturer Part Number: at94k40al
• Description: At94kal Series Field Programmable System Level Integrated Circuit
• Manufacturer: ATMEL Corporation

4.28.4
4.28.4.1
1138I–FPSLI–1/08
16-bit x 16-bit = 32-bit Operation
Example 4 – Basic Usage 16-bit x 16-bit = 32-bit Integer Multiply
Below is an example of how to call the 16 x 16 = 32 multiply subroutine. This is also illustrated in
Figure
Figure 4-39. 16-bit Multiplication, 32-bit Result
The 32-bit result of the unsigned multiplication of 672 and 1844 will now be in the registers
R19:R18:R17:R16. If “muls16x16_32” is called instead of “mul16x16_32”, a signed multiplication
will be executed. If “mul16x16_16” is called, the result will only be 16 bits long and will be stored
in the register pair R17:R16. In this example, the 16-bit result will not be correct.
ldi R23,HIGH(672)
ldi R22,LOW(672) ; Load the number 672 into r23:r22
ldi R21,HIGH(1844)
ldi R20,LOW(1844); Load the number 1844 into r21:r20
callmul16x16_32
4-39.
; multiply routine
; Call 16bits x 16bits = 32bits
AH AL
+
+
=
(sign
(sign
CH
AH * BH
ext)
ext)
CMH
AL * BH
AH * BL
X
BH BL
CML
AL * BL
AT94KAL Series FPSLIC
CL
1 + 2
3
4
117