Answers Database
XBLOX: ACCUM - effects of LOAD on C_OUT and OVFL
Record #2726
Product Family: Software
Product Line: XACT FPGA
Product Part: xblox
Problem Title:
XBLOX: ACCUM - effects of LOAD on C_OUT and OVFL
Problem Description:
Urgency: standard
General Description:
What is the effect on the C_OUT and OVFL outputs of asserting LOAD on the
XBLOX ACCUM macro?
Solution 1:
The synchronous LOAD function of the XBLOX ACCUM macro is implemented via a
2-to-1 multiplexer. The LOAD signal acts as the select line on the mux.
When LOAD is high, the mux passes the B input to the ACCUM register; when
LOAD is low, the mux passes the ADD/SUB value to the ACCUM register.
LOAD has no direct effect on the C_OUT and OVFL outputs. During a LOAD
operation, the C_OUT and OVFL outputs will continue to reflect the carry
out and overflow status of the ADD/SUB logic. However, since LOAD affects
Q_OUT, which drives the A input of the ADD/SUB logic, it does affect C_OUT
and OVFL indirectly.
End of Record #2726 - Last Modified: 05/19/99 14:51 |
