RM0440 Rev 4 471/2126
RM0440 CORDIC co-processor (CORDIC)
485
Arctangent
This function calculates the arctangent, or inverse tangent, of the input argument x.
The primary argument, ARG1, is the input value, x = tan θ. If |x| > 1, a scaling factor of 2
-n
must be applied in software such that -1 < x ∙ 2
-n
< 1. The scaled value x ∙ 2
-n
is programmed
in ARG1 and the scale factor n must be programmed in the SCALE parameter.
Note that the maximum input value allowed is tan θ = 128, which corresponds to an angle
θ = 89.55 degrees. For |x| > 128, a software method must be used to find tan
-1
x.
The secondary argument, ARG2, is unused.
The primary result, RES1, is the angle θ = tan
-1
x. RES1 must be multiplied by 2
n
∙π to
obtain the angle in radians.
The secondary result, RES2, is unused.
Hyperbolic cosine
This function calculates the hyperbolic cosine of a hyperbolic angle x. It can also be used to
calculate the exponential functions e
x
= cosh x + sinh x, and e
-x
= cosh x - sinh x.
The primary argument is the hyperbolic angle x. Only values of x in the range -1.118 to
+1.118 are supported. Since the minimum value of cosh x is 1, which is beyond the range of
the q1.31 format, a scaling factor of 2
-n
must be applied in software. The factor n = 1 must
be programmed in the SCALE parameter.
The secondary argument is not used.
Table 107. Arctangent parameters
Parameter Description Range
ARG1
[-1, 1]
ARG2 Not applicable -
RES1 2
-n
∙tan
-1
x, in radians, divided by p [-1, 1]
RES2 Not applicable -
SCALE n [0 7]
Table 108. Hyperbolic cosine parameters
Parameter Description Range
ARG1
[-0.559 0.559]
ARG2 Not applicable -
RES1
[0.5 0.846]
RES2
[-0.683 0.683]
SCALE n 1
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