Specifications

Intel
®
Quark Core—System Register Organization
Intel
®
Quark SoC X1000 Core
Developer’s Manual October 2013
54 Order Number: 329679-001US
4.5.2 Floating-Point Tag Word
The tag word marks the content of each numeric data register, as shown in Figure 16.
Each two-bit tag represents one of the eight data registers. The principal function of
the tag word is to optimize the FPU’s performance and stack handling by making it
possible to distinguish between empty and non-empty register locations. It also
enables exception handlers to check the contents of a stack location without the need
to perform complex decoding of the actual data.
Figure 16. Floating-Point Tag Word
4.5.3 Floating-Point Status Word
The 16-bit status word reflects the overall state of the FPU. The status word is shown in
Figure 17 and is located in the status register.
A5151-01
Note:
The index i of tag(i) is not top-relative. A program typically uses the "top" field of Status Word to
determine which tag(i) field refers to logical top of stack.
Tag Values:
015
Tag (0)Tag (1)Tag (2)Tag (3)Tag (4)Tag (5)Tag (6)Tag (7)
00 = Valid
01 = Zero
10 = QNaN, SNaN, Infinity, Denormal, and Unsupported Formats
11 = Empty