2.4 IIR Filter DSP Unit
83
This bit cannot be written to while the DSP unit is executing calculations (when the BF bit=1).
[Bit 4] BF (Busy flag)
This bit is read-only. No value may be written.
When the BF=1, the sum-of-products calculator is executing calculations, and no write operations
are allowed to MCSR register bits 15 to 5, or to the MCCR register.
When the BF=0, the sum-of-products register is not operating. Read access to the sum-of-products
output register (MDOR) should be made when this status is indicated.
The BF bit is automatically set to 1 when the MAE and TRG bit are set to 1 to start execution of
sum-of-products calculation. It returns to 0 when sum-of-products calculation is ended.
The BF bit is forcibly cleared to 0 when the MAE bit is set to 0.
[Bit 3, 2] BNK1, BNK0 (Bank bits)
These bits determine the executing bank. For continuous sum-of-products execution over more than
one bank, the value should be that of the first bank.
The initial value of this bit is undefined. It must always be set prior to calculation.
This bit cannot be written to while the DSP unit is executing calculations (when the BF bit=1).
[Bit 1] TRG (Trigger bit)
The TRG bit indicates the start of sum-of-product calculator operation.
When '1' is written to this bit while in sum-of-products enable status (MAE=1), the DSP unit starts
sum-of-products calculation, and the busy flag (BF bit) is set to 1 to indicate that execution is in
progress.
Writing '0' to the TRG bit has no effect.
When MAE=0, or while sum-of-products calculation is in progress (BF=1), writing '1' to the TRG
bit has no effect.
The TRG bit always has the read value '0.'
[Bit 0] MAE (MAC enable bit)
When this bit is set to 1 and the sum-of-products calculator is not operating (BF=0), the DSP unit is
in sum-of-products standby status. In this status, the DSP unit will start sum-of-products calculation
when '1' is written to the TRG bit.
When this bit is set to 0, the DSP unit is in sum-of-products stop status. It is also possible to forcibly
stop sum-of-products calculations even during execution by writing 0 to the MAE bit. This will
cause the DSP unit to cut off sum-of-products calculation and clear the BF bit.
This bit is initialized to 0 after reset.
0
1
0
1
0
1
A
B
C
D
Bank used
BNK1,0