Changed cacti RC delay function to better match cacti code in bitcell. Sense amp also has similar changed but is missing transconductance parameter.

compiler/base/hierarchy_spice.py

@@ -430,7 +430,8 @@ class spice():
         r_wire = self.module_wire_r()
 
         tf = rd*(c_intrinsic+c_load+c_wire)+r_wire*(c_load+c_wire/2)
-        this_delay = self.cacti_rc_delay(inrisetime, tf, 0.5, 0.5, True)
+        extra_param_dict={'vdd': corner[1]} #voltage is second in PVT corner
+        this_delay = self.cacti_rc_delay(inrisetime, tf, 0.5, 0.5, True, extra_param_dict)
         inrisetime = this_delay / (1.0 - 0.5)
         return delay_data(this_delay, inrisetime)
 
@@ -523,7 +524,8 @@ class spice():
                  tf,            # time constant of gate
                  vs1,           # threshold voltage
                  vs2,           # threshold voltage
-                 rise):         # whether input rises or fall
+                 rise,          # whether input rises or fall
+                 extra_param_dict=None):         
 )       """By default, CACTI delay uses horowitz for gate delay.
            Can be overriden in cases like bitline if equation is different.
         """

compiler/bitcells/bitcell_base.py

@@ -252,13 +252,16 @@ class bitcell_base(design.design):
         cells_in_col = OPTS.num_words/OPTS.words_per_row
         return cells_in_col*self.height*spice["wire_r_per_um"]   
         
-    def cacti_rc_delay(self, inputramptime, tf, vs1, vs2, rise): 
+    def cacti_rc_delay(self, inputramptime, tf, vs1, vs2, rise, extra_param_dict): 
 )       """ Special RC delay function used by CACTI for bitline delay
         """
         import math
-        vdd = 5 # temp value
-        if tf > 0.5*(vdd-spice["nom_threshold"])/rise:
-            delay = tf + (vdd-spice["nom_threshold"])/(2*rise)
+        vdd = extra_param_dict['vdd'] 
+        m = vdd / inrisetime #v_wl = vdd for OpenRAM
+        # vdd == V_b_pre in OpenRAM. Bitline swing is assumed 10% of vdd
+        tstep = tf * math.log(vdd/(vdd - 0.1*vdd))
+        if tstep > 0.5*(vdd-spice["nom_threshold"])/m:
+            delay = tstep + (vdd-spice["nom_threshold"])/(2*m)
         else:
-            delay = math.sqrt(2*tf*(vdd-spice["nom_threshold"])/rise)
+            delay = math.sqrt(2*tstep*(vdd-spice["nom_threshold"])/m)
         return delay  

compiler/custom/sense_amp.py

@@ -109,15 +109,15 @@ class sense_amp(design.design):
                                       mult)                               
         return nmos_drain_c + pmos_drain_c + bl_pmos_drain_c
 
-    def cacti_rc_delay(self, inputramptime, tf, vs1, vs2, rise): 
+    def cacti_rc_delay(self, inputramptime, tf, vs1, vs2, rise, extra_param_dict): 
 )       """ Special RC delay function used by CACTI for sense amp delay
         """
         import math
         
         # FIXME: temp values
-        c_senseamp = 0
+        c_senseamp = extra_param_dict['load']
+        vdd = extra_param_dict['vdd'] 
         g_m = 1
         tau = c_senseamp/g_m
-        vdd = 5
         v_sense = 1
-        return tau*math.log(vdd/v_sense)
+        return tau*math.log(vdd/(0.1*vdd))