
2.4 IIR Filter DSP Unit
87
(6) X0-X3 (Input data register)
This register consists of a group of registers with 4-word configuration from X0 to X3, and contains
input data to be used for sum-of-products calculation.
The X register contains input data in 16-bit length integer format.
The X register has 4 banks of 4 words each, with a bank bit to determine which bank is used in sum-
of-products calculation.
X initial value register is undefined.
Write access to the X register is by means of a shift register, so that only the X0 area is write-
enabled. Each time data is written to X0, the previous data is shifted to X1 through X3 in order.
This register cannot be simultaneously accessed from both the DSP and the CPU, so that reading
and writing should not be attempted during execution. If read or write access is attempted during
execution, neither the contents of the register nor the calculation results are assured.
This register is not enabled for byte access. Always access in word units at even-numbered
addresses.
All areas of this register are enabled for read access to each address, however the lower 3 bits of any
write values will be ignored (see example).
(7) Y0 to Y3 (Input data register)
This register consists of a group of registers with 4-word configuration from Y0 to Y3, and contains
output data to be used for sum-of-products calculation.
The Y register contains input data in 16-bit length integer format.
The Y register has 4 banks of 4 words each, with a bank bit to determine which bank is used in sum-
of-products calculation.
Y register initial values are undefined.
Write access to the Y register is made by means of a shift register, so that only the Y0 area is write-
enabled. Each time data is written to Y0, the previous data is shifted to Y1 through Y3 in order.
This register cannot be simultaneously accessed from both the DSP and the CPU, so that reading
A0
A1
A2
A0
A1
A2
A0
A1
A2
Address 00 1940H
X0
X1
X2
X3
Address 00 1942H
Address 00 1944H
Address 00 1946H
1948H
194AH
194CH
194EH
1958H
195AH
195CH
195EH
1950H
1952H
1954H
1956H
Initial Value
(undefined)
15
0
A0
A1
A2
A0
A1
A2
A0
A1
A2
Address 00 1960H
Y0
Y1
Y2
Y3
Address 00 1962H
Address 00 1964H
Address 00 1966H
1968H
196AH
196CH
196EH
1978H
197AH
197CH
197EH
1970H
1972H
1974H
1976H
Initial Value
(undefined)
15
0