Mostly upbeat corporate earnings from John Deere ( DE ) and Hewlett Packard ( HPQ ) also contributed to the firmer tone before equities surrendered their minimal gains after the CPI data. U.S. stock futures slipped into negative territory Friday morning as an above-consensus 0.3% gain in the core consumer-price index was seen as giving the Federal Reserve more ammunition to raise interest rates in September. Ahead of Friday's single economic data point, stock futures had been cautiously higher, buoyed by firm overseas markets and expectations for global central banks to remain accommodative.