Expanded micro-operation parameters (added dedicated control bit to force the B input of

the modular multiplier to 1, this is necessary to bring numbers out of Montgomery domain).

1 files changed, 15 insertions, 0 deletions

diff --git a/rtl/modexpng_microcode.vh b/rtl/modexpng_microcode.vh
index af21391..1465c48 100644
--- a/rtl/modexpng_microcode.vh
+++ b/rtl/modexpng_microcode.vh
@@ -17,15 +17,30 @@ localparam UOP_W = UOP_OPCODE_W + UOP_CRT_W + UOP_NPQ_W + UOP_AUX_W + UOP_LADDER
 
 // OPCODE
 localparam [UOP_OPCODE_W -1:0] UOP_OPCODE_STOP               = 4'd0;
+/* all fields are don't care
+ */
 
 localparam [UOP_OPCODE_W -1:0] UOP_OPCODE_INPUT_TO_WIDE      = 4'd1;
 localparam [UOP_OPCODE_W -1:0] UOP_OPCODE_INPUT_TO_NARROW    = 4'd2;
+/* CRT tells into which of the dual MMM to write
+ * NPQ specifies the width of the operand
+ * AUX specifies from which INPUT to read
+ * LADDER is don't care
+ * source WIDE is always don't care
+ * destination NARROW is don't care for _WIDE opcode and vice versa
+ * 
+*/
 
 localparam [UOP_OPCODE_W -1:0] UOP_OPCODE_OUTPUT_FROM_NARROW = 4'd3;
 
 //localparam [UOP_OPCODE_W -1:0] UOP_OPCODE_COPY_CRT_Y2X  = 4'd0;
 
 localparam [UOP_OPCODE_W -1:0] UOP_OPCODE_MODULAR_MULTIPLY   = 4'd8;
+/* CRT is don't care
+ * NPQ specifies the width of the operand
+ * AUX = AUX_2 forces B input to 1 (AUX_1 reads from source NARROW as usual)
+ * LADDER specifies Montgomery ladder mode 
+ */
 
 // CRT
 localparam [UOP_CRT_W -1:0] UOP_CRT_X   = 1'b0;