at94k05al-25aqi ATMEL Corporation, at94k05al-25aqi Datasheet - Page 110

• Manufacturer Part Number: at94k05al-25aqi
• Description: 5k - 40k Gates Of At40k Fpga With 8-bit Microcontroller, Up To 36k Bytes Of Sram And On-chip Jtag Ice
• Manufacturer: ATMEL Corporation

16-bit x 16-bit = 32-bit
Operation
Example 4 –
Basic Usage
16-bit x 16-bit = 32-bit
Integer Multiply
110
AT94K Series FPSLIC
Below is an example of how to call the 16 x 16 = 32 multiply subroutine. This is also illustrated
in Figure 62.
Figure 62. 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 multiplica-
tion 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
; multiply routine
; Call 16bits x 16bits = 32bits
AH AL
+
+
=
(sign
(sign
AH * BH
CH
ext)
ext)
CMH
AL * BH
AH * BL
X
BH BL
CML
AL * BL
CL
1 + 2
3
4
Rev. 1138F–FPSLI–06/02