Input Formats; Mac Input/Output Registers; Mr Register Operation - Analog Devices adsp-2100 Manual

2 Computational Units

2.3.2.2 Input Formats

To facilitate multiprecision multiplications, the multiplier accepts X and Y
inputs represented in any combination of signed twos-complement format
and unsigned format.
X input
signed
unsigned
signed
unsigned
The input formats are specified as part of the instruction. These are
dynamically selectable each time the multiplier is used.
The (signed x signed) mode is used when multiplying two signed single
precision numbers or the two upper portions of two signed multiprecision
numbers.
The (unsigned x signed) and (signed x unsigned) modes are used when
multiplying the upper portion of a signed multiprecision number with the
lower portion of another or when multiplying a signed single precision
number by an unsigned single precision number.
The (unsigned x unsigned) mode is used when multiplying unsigned
single precision numbers or the non-upper portions of two signed
multiprecision numbers.

2.3.2.3 MAC Input/Output Registers

The sources of MAC input and output are:
Source for
X input port
MX0, MX1
AR
MR0, MR1, MR2
SR0, SR1

2.3.2.4 MR Register Operation

As described, and shown on the block diagram, the MR register is divided
into three sections: MR0 (bits 0-15), MR1 (bits 16-31), and MR2 (bits 32-
39). Each of these registers can be loaded from the DMD bus and output to
the R bus or the DMD bus.
2 – 18
Y input
x signed
signed
x
x unsigned
unsigned
x
Source for
Y input port
MY0, MY1
MF
Destination for
R output port
MR (MR2, MR1, MR0)
MF