Calculation of Number of embedded multiplier

[Altera_Forum]

Operation: z<= a*b; 

 Therer are 2 cases below and I need someone to explain on how the number below obtained. Pls explain the reason there are uses of mixed sign, unsigned and signed multiplier since this is just a signed operation. thanks   Case1:  input signed [31:0] b;  input signed [31:0] a;  (*multstyle = "dsp"*) output reg signed [63:0]z;    Simple Multipliers (9-bit) 0  Simple Multipliers (18-bit) 4  Embedded Multiplier Blocks --  Embedded Multiplier 9-bit elements 8  Signed Embedded Multipliers 1  Unsigned Embedded Multipliers 1  Mixed Sign Embedded Multipliers 2  Variable Sign Embedded Multipliers 0  Dedicated Input Shift Register Chains 0   Case2    input signed [31:0] b;  input signed [31:0] a;  (*multstyle = "dsp"*) output reg signed [31:0]z;    Simple Multipliers (9-bit) 0  Simple Multipliers (18-bit) 3  Embedded Multiplier Blocks --  Embedded Multiplier 9-bit elements 6  Signed Embedded Multipliers 0  Unsigned Embedded Multipliers 1  Mixed Sign Embedded Multipliers 2  Variable Sign Embedded Multipliers 0  Dedicated Input Shift Register Chains 0

[Altera_Forum]

Since the device's multipliers can only handle 18x18 multiplications, larger multiplications are implemented using several partial multiplications, like you learned in school. 

 Thus, a full 32x32 multiplication requires 4 partial multiplcations. And since the signal is in the MSB, the other parts are handled as unsigned. 1st a[17:0] * b [17:0] - unsigned * unsigned 2nd a[31:18] * b [17:0] - signed * unsigned 3rd a[17:0] * b [31:18] - unsigned * signed 4th a[31:18] * b [31:18] - signed * signed  Thus, the mix you're seeing in the report.  As for case 2, since you're only keeping the result's 32 LSBs, the 4th term isn't needed.