Maxim Integrated MAX31782 - Manual (Page 121)

MaximIntegrated 14-6
MAX31782 User’s Guide
Revision 0; 8/11
14.5.1MultiplierControlRegister(MCNT)
Bit 7 6 5 4 3 2 1 0
Name OF MCW CLD SQU OPCS MSUB MMAC SUS
Reset 0 0 0 0 0 0 0 0
Access r rw rw rw rw rw rw rw
BIT NAME DESCRIPTION
7 OF
OverflowFlag . This bit is set to logic 1 when an overflow occurred for the last operation . This bit can be
set for accumulation/subtraction operations or unsigned multiply-negate attempts . This bit is automatically
cleared to 0 following a reset, starting a multiplier operation, or setting of the CLD bit to 0 .
6 MCW
MCRegisterWriteSelect . The state of the MCW bit determines if an operation result will be placed into
the accumulator registers (MC) .
0 = The result will be written to the MC registers .
1 = The result is not written to the MC registers (MC register content is unchanged) .
5 CLD
ClearDataregister . This bit initializes the operand registers and the accumulator of the multiplier . When it
is set to 1, the contents of all data registers and the OF bit are cleared to 0 and the operand load counter
is reset immediately . This bit is cleared by hardware automatically . Writing a 0 to this bit has no effect .
4 SQU
SquareFunctionEnable . This bit supports the hardware square function . When this bit is set to logic 1, a
square operation is initiated after an operand is written to either the MA or the MB register . Writing data to
either of the operand registers writes to both registers and triggers the specified square or square-accu-
mulate/subtract operation . Setting this bit to 1 also overrides the OPCS bit setting . When SQU is cleared to
logic 0, the hardware square function is disabled .
0 = Square function disabled
1 = Square function enabled
3 OPCS
OperandCountSelect . This bit defines how many operands must be loaded to trigger a multiply or multi-
ply-accumulate/subtract operation (except when SQU = 1, since this implicitly specifies a single operand) .
When this bit is cleared to logic 0, both operands (MA and MB) must be written to trigger the operation .
When this bit is set to 1, the specified operation is triggered once either operand is written .
0 = Both operands (MA and MB) must be written to trigger the multiplier operation .
1 = Loading one operand (MA or MB) triggers the multiplier operation .
2 MSUB
Multiply-AccumulateNegate . Configuring this bit to logic 1 enables negation of the product for signed
multiply operations and subtraction of the product from the accumulator (MC[2:0]) when MMAC = 1 . When
MSUB is configured to logic 0, the product of multiply operations will not be negated and accumulation is
selected when MMAC = 1 .
1 MMAC
Multiply-AccumulateEnable . This bit enables the accumulate or subtract operation (as per MSUB) for
the hardware multiplier . When this bit is cleared to logic 0, the multiplier performs only multiply operations .
When this bit is set to logic 1, the multiplier performs a multiply-accumulate or multiply-subtract operation
based upon the MSUB bit .
0 = Accumulate/subtract operation disabled
1 = Accumulate/subtract operation enabled
0 SUS
Signed-Unsigned . This bit determines the data type of the operands . When this bit is cleared to logic
0, the operands are treated as two’s complement values and the multiplier performs a signed operation .
When this bit is set to logic 1, the operands are treated as absolute magnitudes and the multiplier per-
forms an unsigned operation .
0 = Signed operands
1 = Unsigned operands