Macc Operation - Xilinx 7 Series User Manual

Appendix A: CARRYOUT, CARRYCASCOUT, and MULTSIGNOUT

MACC Operation

CARRYOUT[3] is invalid in the MACC operation.
CARRYCASCOUT and MULTSIGNOUT: Hardware and software do not match due to
modeling difference. The software simulation model is an abstraction of the hardware
model. The software views of CARRYCASCOUT and MULTSIGNOUT enable
higher-precision MACC functions to be built in the UNISIM model. They are not logically
equivalent to hardware CARRYCASCOUT and MULTSIGNOUT. Only the hardware and
software results (P output) are logically equivalent. The internal signals
(CARRYCASCOUT and MULTSIGNOUT) are not. See
X-Ref Target - Figure A-5
58
Send Feedback
Software Model
A
x
B
CARRYIN
Zmux (e.g., C, P, PCIN)
Hardware Implementation
A
x
B
CARRYIN
Zmux (e.g., C, P, PCIN)
Partial products from the multiply operation are added together in the second stage ternary adder.
Figure A-5: MACC Software and Hardware Models
www.xilinx.com
Figure A-5.
MULTSIGNOUT
CARRYCASCOUT
+
P[47:0]
MULTSIGNOUT
CARRYCASCOUT
+
P[47:0]
7 Series DSP48E1 User Guide
UG479 (v1.10) March 27, 2018
UG369_A_05_111208