XC886/888CLM
CORDIC Coprocessor
User’s Manual
11-4
V1.3, 2010-02
CORDIC Coprocessor, V 1.2.1
11.2.2
Interrupt
The End-of-Calculation (EOC) is the only interrupt source of the CORDIC Coprocessor.
If interrupt is enabled by CD_STATC.INT_EN = 1, an interrupt request signal is activated
at the end of CORDIC calculation and also indicated by the CD_STATC.EOC flag. If not
cleared by software, the EOC flag remains set until cleared by hardware when a read
access is performed to the low byte of Z result data (DMAP = 0).
During EOC data processing, a check must be made to ensure that the ERROR flag is
not set (indicates data overflow has occurred).
11.2.3
Normalized Result Data
In all operating modes, the CORDIC Coprocessor returns a normalized result data for X
and Y, as shown in the following equation:
On the other hand, the interpretation for Z result data differs, which is also dependent on
the CORDIC function used:
For
linear
function, there is no additional processing of the CORDIC calculated Z data,
as such it is taken directly as the result data. The accessible Z result data is a real
number expressed as signed 4Q16.
For
circular
and
hyperbolic
functions, the accessible Z result data is a normalized
integer value, angles in the range [-
π
,((2
15
-1)/2
15
)
π
] are represented by [-2
15
,(2
15
-1)]. The
CORDIC Coprocessor expects Z data to be interpreted with this scaling:
The CORDIC calculated data includes an inherent gain factor
Κ
resulting from the
rotation or vectoring. The value
Κ
is different for each CORDIC function, as shown in
.
Table 11-1
CORDIC Function Inherent Gain Factor for Result Data
Function
Approximated Gain K
Circular
1.64676
Hyperbolic
0.828
Linear
1
X or Y Result Data =
CORDIC Calculated Data
MPS
Input Z Initial Data =
32768
π
Real Z Initial Value (in radians) x
Real Z Result Value (in radians) =
32768
π
Z Result Data x
*
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