18.4. Modes of operation

The VFP9-S coprocessor provides full IEEE 754 standard compatibility through a combination of hardware and software. There are rare cases that require significant additional compute time to resolve correctly according to the requirements of the IEEE 754 standard. For instance, the VFP9-S coprocessor does not process subnormal input values directly. To provide correct handling of subnormal inputs according to the IEEE 754 standard, a trap is made to support code to process the operation. Using the support code for processing this operation can require hundreds of cycles. In some applications this is unavoidable, because compliance with the IEEE 754 standard is essential to proper operation of the program. In many other applications, especially in the embedded market, strict compliance to the IEEE 754 standard is unnecessary, while determinable runtime, low interrupt latency, and low power are of more importance. The following sections describe the two VFP9-S coprocessor modes of operation:

Copyright © 2004, 2006 ARM Limited. All rights reserved.ARM DDI 0287B