implemented basic attenuator range function (but not in cal funcs)

4 files changed, 142 insertions, 99 deletions

diff --git a/device-functions.c b/device-functions.c
index a590830..2376e5a 100644
--- a/device-functions.c
+++ b/device-functions.c
@@ -192,7 +192,7 @@ int Set_Amplitude(int check_possible_only,int pol_override,int override_on,int w
                   int switch_range_only,int channel,float new_ampl,int called_from_set_pw)
 {
 	int word_out;	  /* what is sent to the DAC */
-	int relay_range,old_range,old_actual_pol;	  /* selects relay range */
+	int relay_range,atten_range,old_range,old_actual_pol;	  /* selects relay range */
 	int UseNegData;	/* if polarity is negative and separate piece-wise linear data is available for neg */
 	int point_found;
 	int entry;
@@ -255,7 +255,7 @@ int Set_Amplitude(int check_possible_only,int pol_override,int override_on,int w
 
 		/* determine the previous relay range */
 		Set_VI_Control(pwl_ampl_values,channel,globals.ChannelState[channel].amplitude,&point_found,
-		               &old_range,&UseNegData,&entry,&word_out,&old_actual_pol);
+		               &old_range,&atten_range,&UseNegData,&entry,&word_out,&old_actual_pol);
 	}
 
 	word_out = -1;
@@ -272,7 +272,7 @@ int Set_Amplitude(int check_possible_only,int pol_override,int override_on,int w
 		/* set the amplitude controls now. */
 		int status;
 		if ((status=Set_VI_Control(pwl_ampl_values,channel,new_ampl,&point_found,
-		                           &relay_range,&UseNegData,&entry,&word_out,&actual_pol))) {
+		                           &relay_range,&atten_range,&UseNegData,&entry,&word_out,&actual_pol))) {
 			return status;
 		}
 	}
@@ -319,6 +319,19 @@ int Set_Amplitude(int check_possible_only,int pol_override,int override_on,int w
 			set_shiftreg_bits(SR_3, POS_13, ONE_BIT, BIT_LOW);	/* set O.POL line low to switch pol relay to -, normally */
 		}
 
+		// Are attenuators used?
+		if (globals.Flash.attenuators[channel][0] > 0.0) {
+			// deal with attenuator range - haven't done for CH2 yet
+
+			// only implement one attenuator so far (range 0), out of possible max_attens (8!)
+			if (atten_range == 0) {
+				set_shiftreg_bits(SR_2, XTR_POS + 5, ONE_BIT, BIT_HIGH);
+			} else {
+				set_shiftreg_bits(SR_2, XTR_POS + 5, ONE_BIT, BIT_LOW);
+			}			
+		}
+printf ("\nAMPL %f, range %d, word %d, atten %d\n\n", new_ampl, relay_range, word_out, atten_range);
+
 	} else {
 
 		if (!globals.Flash.ampl_ranges_for_ch2_only) {
@@ -368,7 +381,7 @@ int Set_Pw(int check_possible_only,int word_override,int range_override,int chan
 {
 	int word_out;  /* what is sent to the DAC */
 	int cap_range_control;
-	int point_found,relay_range,UseNegData,entry;
+	int point_found,relay_range,dummy,UseNegData,entry;
 	int status,actual_pol;
 
 	/* abandon if high channel selected by user but not enabled by firmware */
@@ -404,7 +417,7 @@ int Set_Pw(int check_possible_only,int word_override,int range_override,int chan
 	} else {
 		/* set the pw controls now. */
 		if ((status=Set_VI_Control(pwl_pw_values,channel,set_pw,&point_found,
-		                           &relay_range,&UseNegData,&entry,&word_out,&actual_pol))) {
+		                           &relay_range,&dummy,&UseNegData,&entry,&word_out,&actual_pol))) {
 			return status;
 		}
 	}
@@ -492,7 +505,7 @@ int Set_Pw(int check_possible_only,int word_override,int range_override,int chan
 	/* use CH2 calibration to do this */
 	if (globals.Flash.is_monocycle[0] && channel==0) {
 		if ((status=Set_VI_Control(pwl_pw_values,1,set_pw,&point_found,
-		                           &relay_range,&UseNegData,&entry,&word_out,&actual_pol))) {
+		                           &relay_range,&dummy,&UseNegData,&entry,&word_out,&actual_pol))) {
 			return status;
 		}
 		set_dac(globals.Flash.monocycle_dac[0],word_out);
@@ -513,7 +526,7 @@ int Set_Offset(int check_possible_only,int override_on,int word_override,int ran
 {
 	int word_out;	  /* what is sent to the DAC */
 	int point_found;
-	int entry,dummy1,dummy2,dummy3;
+	int entry,dummy0,dummy1,dummy2,dummy3;
 	int actual_pol;
 	int old_range,relay_range;
 
@@ -541,7 +554,7 @@ int Set_Offset(int check_possible_only,int override_on,int word_override,int ran
 
 		/* determine the previous relay range */
 		Set_VI_Control(pwl_os_values,channel,globals.ChannelState[channel].offset,&point_found,
-		               &old_range,&dummy1,&dummy2,&word_out,&dummy3);
+		               &old_range,&dummy0,&dummy1,&dummy2,&word_out,&dummy3);
 	}
 
 	if (override_on) {
@@ -550,7 +563,7 @@ int Set_Offset(int check_possible_only,int override_on,int word_override,int ran
 	} else {
 		int status;
 		if ((status=Set_VI_Control(pwl_os_values,channel,new_offset,&point_found,
-		                           &relay_range,&dummy2,&entry,&word_out,&actual_pol))) {
+		                           &relay_range,&dummy0,&dummy2,&entry,&word_out,&actual_pol))) {
 			return status;
 		}
 	}
@@ -595,7 +608,7 @@ int Set_Offset(int check_possible_only,int override_on,int word_override,int ran
 int Set_frequency(int check_possible_only,int word_override,int range_override,int channel,float set_freq)
 {
 	float new_pw;
-	int point_found,relay_range,UseNegData,entry,actual_pol,old_range;
+	int point_found,relay_range,UseNegData,entry,actual_pol,old_range,dummy;
 	int word_out;	/* what is sent to the DAC */
 
 	/* abandon if high channel selected by user but not enabled by firmware */
@@ -626,7 +639,7 @@ int Set_frequency(int check_possible_only,int word_override,int range_override,i
 		/* added Feb 23/05 */
 		/* determine the previous relay range */
 		Set_VI_Control(pwl_period_values,channel,1.0/globals.ChannelState[channel].frequency,&point_found,
-		               &old_range,&UseNegData,&entry,&word_out,&actual_pol);
+		               &old_range,&dummy,&UseNegData,&entry,&word_out,&actual_pol);
 	}
 
 	/* find appropriate range/fine settings from piece-wise linear data in flash memory */
@@ -637,7 +650,7 @@ int Set_frequency(int check_possible_only,int word_override,int range_override,i
 		/* set the amplitude controls now. */
 		int status;
 		if ((status=Set_VI_Control(pwl_period_values,channel,1.0/set_freq,&point_found,
-		                           &relay_range,&UseNegData,&entry,&word_out,&actual_pol))) {
+		                           &relay_range,&dummy,&UseNegData,&entry,&word_out,&actual_pol))) {
 			return status;
 		}
 	}
@@ -694,7 +707,7 @@ int Set_Delay(int check_possible_only,int word_override,int range_override,int c
 	int word_out;  /* what is sent to the DAC */
 	int cap_range_control;	/* what is actually sent to shift register */
 	float setting;
-	int point_found,relay_range,UseNegData,entry,actual_pol;
+	int point_found,relay_range,UseNegData,entry,actual_pol,dummy;
 
 	/* abandon if high channel selected by user but not enabled by firmware */
 	if (channel && !globals.Flash.ChanKey_delay) {
@@ -743,7 +756,7 @@ int Set_Delay(int check_possible_only,int word_override,int range_override,int c
 		/* set the amplitude controls now. */
 		int status;
 		if ((status=Set_VI_Control(pwl_delay_values,channel,setting,&point_found,
-		                           &relay_range,&UseNegData,&entry,&word_out,&actual_pol))) {
+		                           &relay_range,&dummy,&UseNegData,&entry,&word_out,&actual_pol))) {
 			return status;
 		}
 	}
@@ -1475,14 +1488,14 @@ int Set_Amp_Calib(int channel,float meas_ampl)
 {
 	float change_ratio;
 	int i,status;
-	int point_found,relay_range,UseNegData,entry,word_out,actual_pol;
+	int point_found,relay_range,UseNegData,entry,word_out,actual_pol,atten_range;
 	int eprom_loc;
 
 	/* use for all channels */
 
 	/* get current range and polarity settings */
 	Set_VI_Control(pwl_ampl_values,channel,globals.ChannelState[channel].amplitude,&point_found,
-	               &relay_range,&UseNegData,&entry,&word_out,&actual_pol);
+	               &relay_range,&atten_range,&UseNegData,&entry,&word_out,&actual_pol);
 
 	if (fabs(globals.ChannelState[channel].amplitude)<globals.Flash.ampl_zero_equiv[channel]) {
 		return NeedNonZeroAmpl;
@@ -1519,13 +1532,13 @@ int Set_Amp_Calib(int channel,float meas_ampl)
 int Set_Mon_Calib(int channel,float meas_ampl)
 {
 	float change_ratio;
-	int point_found,relay_range,UseNegData,entry,word_out,actual_pol,eprom_loc;
+	int point_found,relay_range,UseNegData,entry,word_out,actual_pol,eprom_loc,atten_range;
 
 	/* use for all channels */
 
 	/* get current range and polarity settings */
 	Set_VI_Control(pwl_ampl_values,channel,globals.ChannelState[channel].amplitude,&point_found,
-	               &relay_range,&UseNegData,&entry,&word_out,&actual_pol);
+	               &relay_range,&atten_range,&UseNegData,&entry,&word_out,&actual_pol);
 
 	if (fabs(globals.ChannelState[channel].Curr_Mon_value)< (5.0 * globals.Flash.monitor_step[channel])) {
 		return NeedNonZeroAmpl;
@@ -2407,7 +2420,7 @@ int Set_VI_Del_Cal(int parameter,int channel,int calibration_point_number)
 }
 
 
-int Set_VI_Control(int parameter,int channel,float new_ampl,int *point_found,int *relay_range,
+int Set_VI_Control(int parameter,int channel,float new_ampl,int *point_found,int *relay_range,int *atten_range,
                    int *UseNegData,int *entry,int *word_out,int *actual_pol)
 {
 	float use_ampl,tweaked_use_ampl,fraction;
@@ -2682,75 +2695,101 @@ int Set_VI_Control(int parameter,int channel,float new_ampl,int *point_found,int
 	*point_found=*relay_range=*entry=0;
 	*word_out=-1;
 
-	tweaked_use_ampl = use_ampl;
+	float use_atten = 1.0;
 
-	for (range_i=starting_range; (range_i<max_ranges) && (!*point_found || top_range_only); ++range_i) {	/* use non-all-zero ranges */
-		/* apply pw ampl/pol tweaks */
-		if (parameter == pwl_pw_values) {
-			tweaked_use_ampl = use_ampl + globals.Flash.pw_range_pol_tweaks[channel][range_i][pw_polarity];
-		}
+	for (*atten_range = max_attens; (*atten_range >= -1) && !(*point_found);) {
 
-		for (entry_i=0; (entry_i<max_points-1) && (!*point_found || top_range_only); ++entry_i) {
-			index=true_channel*max_ranges*max_polarity*max_points
-			      +(range_i)*max_polarity*max_points
-			      +(*UseNegData)*max_points
-			      +(entry_i);
+		(*atten_range)--;
 
-			if ( (fabs(pwl_amp[index]-pwl_amp[index+1])>smallest_allowed_number)
-			                &&
-			                (	((tweaked_use_ampl>=pwl_amp[index]) &&	(tweaked_use_ampl<=pwl_amp[index+1]))
-			                        ||
-			                        (decreasing_values_allowed && (tweaked_use_ampl<=pwl_amp[index]) &&	(tweaked_use_ampl>=pwl_amp[index+1]))  /* for OS only */
-			                )
-			   ) {
-				*point_found=1;
+		if (*atten_range == -1) {
+			// no valid attenuators
+			use_atten = 1.0;
+		} else {
+		
+			if (parameter != pwl_ampl_values) {
+                 		continue;
+			} else if (globals.Flash.attenuators[channel][*atten_range] == 0.0) {
+				continue;
+			} else {
+				use_atten = globals.Flash.attenuators[channel][*atten_range];
+			}
+		}
+
+		for (range_i=starting_range; (range_i<max_ranges) && (!*point_found || top_range_only); ++range_i) {	/* use non-all-zero ranges */
+			/* apply pw ampl/pol tweaks */
+			if (parameter == pwl_pw_values) {
+				// tweak pw shifts
+				tweaked_use_ampl = use_ampl + globals.Flash.pw_range_pol_tweaks[channel][range_i][pw_polarity];
+			} else if (parameter == pwl_ampl_values) {
+				// compensate for attenuators
+				tweaked_use_ampl = use_ampl * use_atten;
+			} else {
+				// no tweaks
+				tweaked_use_ampl = use_ampl;
+			}
 
-				if ((parameter==pwl_ampl_values) && globals.Flash.ampl_os_ranges_related[channel]) {
-					for (i=0; i<points_in_range; i++) {
-						if (max_os_in_range<globals.Flash.os_pwl_amp[channel][range_i][0][i]) {
-							max_os_in_range=globals.Flash.os_pwl_amp[channel][range_i][0][i];
+			for (entry_i=0; (entry_i<max_points-1) && (!*point_found || top_range_only); ++entry_i) {
+				index=true_channel*max_ranges*max_polarity*max_points
+				      +(range_i)*max_polarity*max_points
+				      +(*UseNegData)*max_points
+				      +(entry_i);
+
+				if ( (fabs(pwl_amp[index]-pwl_amp[index+1])>smallest_allowed_number)
+				                &&
+				                (	((tweaked_use_ampl>=pwl_amp[index]) &&	(tweaked_use_ampl<=pwl_amp[index+1]))
+				                        ||
+				                        (decreasing_values_allowed && (tweaked_use_ampl<=pwl_amp[index]) &&	(tweaked_use_ampl>=pwl_amp[index+1]))  /* for OS only */
+				                )
+				   ) {
+					*point_found=1;
+
+					if ((parameter==pwl_ampl_values) && globals.Flash.ampl_os_ranges_related[channel]) {
+						for (i=0; i<points_in_range; i++) {
+							if (max_os_in_range<globals.Flash.os_pwl_amp[channel][range_i][0][i]) {
+								max_os_in_range=globals.Flash.os_pwl_amp[channel][range_i][0][i];
+							}
+							if (min_os_in_range>globals.Flash.os_pwl_amp[channel][range_i][0][i]) {
+								min_os_in_range=globals.Flash.os_pwl_amp[channel][range_i][0][i];
+							}
 						}
-						if (min_os_in_range>globals.Flash.os_pwl_amp[channel][range_i][0][i]) {
-							min_os_in_range=globals.Flash.os_pwl_amp[channel][range_i][0][i];
+						if ((globals.ChannelState[channel].offset<min_os_in_range) || (globals.ChannelState[channel].offset>max_os_in_range)) {
+							*point_found=0;	/* try higher range if can't satisfy os and ampl both in this range */
 						}
 					}
-					if ((globals.ChannelState[channel].offset<min_os_in_range) || (globals.ChannelState[channel].offset>max_os_in_range)) {
-						*point_found=0;	/* try higher range if can't satisfy os and ampl both in this range */
-					}
-				}
 
-				if ((parameter==pwl_os_values) && globals.Flash.ampl_os_ranges_related[channel]) {
-					for (i=0; i<points_in_range; i++) {
-						if (max_ampl_in_range<globals.Flash.ampl_pwl_amp[channel][range_i][*UseNegData][i]) {
-							max_ampl_in_range=globals.Flash.ampl_pwl_amp[channel][range_i][*UseNegData][i];
+					if ((parameter==pwl_os_values) && globals.Flash.ampl_os_ranges_related[channel]) {
+						for (i=0; i<points_in_range; i++) {
+							if (max_ampl_in_range<globals.Flash.ampl_pwl_amp[channel][range_i][*UseNegData][i]) {
+								max_ampl_in_range=globals.Flash.ampl_pwl_amp[channel][range_i][*UseNegData][i];
+							}
+							if (min_ampl_in_range>globals.Flash.ampl_pwl_amp[channel][range_i][*UseNegData][i]) {
+								min_ampl_in_range=globals.Flash.ampl_pwl_amp[channel][range_i][*UseNegData][i];
+							}
 						}
-						if (min_ampl_in_range>globals.Flash.ampl_pwl_amp[channel][range_i][*UseNegData][i]) {
-							min_ampl_in_range=globals.Flash.ampl_pwl_amp[channel][range_i][*UseNegData][i];
+						if ((fabs(globals.ChannelState[channel].amplitude)<min_ampl_in_range) || (fabs(globals.ChannelState[channel].amplitude)>max_ampl_in_range)) {
+							*point_found=0;	/* try higher range if can't satisfy os and ampl both in this range */
 						}
 					}
-					if ((fabs(globals.ChannelState[channel].amplitude)<min_ampl_in_range) || (fabs(globals.ChannelState[channel].amplitude)>max_ampl_in_range)) {
-						*point_found=0;	/* try higher range if can't satisfy os and ampl both in this range */
-					}
-				}
 
-				fraction = (tweaked_use_ampl-pwl_amp[index]) / (pwl_amp[index] - pwl_amp[index+1]);
-				*relay_range=range_i;
-				*entry=entry_i;
+					fraction = (tweaked_use_ampl-pwl_amp[index]) / (pwl_amp[index] - pwl_amp[index+1]);
+					*relay_range=range_i;
+					*entry=entry_i;
 
-				/* check for linear voltage-controlled PW */
-				if (	(parameter==pwl_pw_values)
-				                && globals.Flash.volt_ctrl_pw[channel]
-				                && (pwl_vc[index] < pwl_vc[index+1])) {
-					reciprocal_relationship=NO;
-				}
+					/* check for linear voltage-controlled PW */
+					if (	(parameter==pwl_pw_values)
+					                && globals.Flash.volt_ctrl_pw[channel]
+					                && (pwl_vc[index] < pwl_vc[index+1])) {
+						reciprocal_relationship=NO;
+					}
 
-				if (reciprocal_relationship) {
-					inverse_word_out = fraction * (1.0/((float) pwl_vc[index]) - 1.0/((float) pwl_vc[index+1]));
-					inverse_word_out+=1/((float) pwl_vc[index]);
-					*word_out=(int) (1.0/inverse_word_out);
-				} else {
-					*word_out = (int) ( fraction * (float) (pwl_vc[index] - pwl_vc[index+1]) );
-					*word_out+=pwl_vc[index];
+					if (reciprocal_relationship) {
+						inverse_word_out = fraction * (1.0/((float) pwl_vc[index]) - 1.0/((float) pwl_vc[index+1]));
+						inverse_word_out+=1/((float) pwl_vc[index]);
+						*word_out=(int) (1.0/inverse_word_out);
+					} else {
+						*word_out = (int) ( fraction * (float) (pwl_vc[index] - pwl_vc[index+1]) );
+						*word_out+=pwl_vc[index];
+					}
 				}
 			}
 		}
@@ -2825,7 +2864,7 @@ int Set_VI_Control(int parameter,int channel,float new_ampl,int *point_found,int
 
 int Set_VI_Add_Cal(int parameter,int channel,float cal_point)
 {
-	int point_found,range,polarity,entry,word_out,total;
+	int point_found,range,polarity,entry,word_out,total,atten_range;
 	int i;
 	float max_in_range;
 	float least_integrated_error,integrated_error;
@@ -2866,7 +2905,7 @@ int Set_VI_Add_Cal(int parameter,int channel,float cal_point)
 		size_of_y_float=sizeof(globals.Flash.ampl_pwl_amp);
 
 		Set_VI_Control(pwl_ampl_values,channel,globals.ChannelState[channel].amplitude,&point_found,
-		               &range,&polarity,&entry,&word_out,&actual_pol);
+		               &range,&atten_range,&polarity,&entry,&word_out,&actual_pol);
 		old_val=globals.ChannelState[channel].amplitude;
 		abs_cal_point=fabs(cal_point);	/* ampl data is positive always */
 
@@ -2887,7 +2926,7 @@ int Set_VI_Add_Cal(int parameter,int channel,float cal_point)
 
 		old_val=globals.ChannelState[channel].offset;
 		Set_VI_Control(pwl_os_values,channel,old_val,&point_found,
-		               &range,&polarity,&entry,&word_out,&actual_pol);
+		               &range,&atten_range,&polarity,&entry,&word_out,&actual_pol);
 		break;
 	case pwl_pw_values:
 		max_polarity=timing_polarities;
@@ -2898,7 +2937,7 @@ int Set_VI_Add_Cal(int parameter,int channel,float cal_point)
 		size_of_y_float=sizeof(globals.Flash.pw_pwl_time);
 		old_val=globals.ChannelState[channel].pw;
 		Set_VI_Control(pwl_pw_values,channel,old_val,&point_found,
-		               &range,&polarity,&entry,&word_out,&actual_pol);
+		               &range,&atten_range,&polarity,&entry,&word_out,&actual_pol);
 		break;
 	case pwl_delay_values:
 		max_polarity=timing_polarities;
@@ -2909,7 +2948,7 @@ int Set_VI_Add_Cal(int parameter,int channel,float cal_point)
 		size_of_y_float=sizeof(globals.Flash.delay_pwl_time);
 		old_val=globals.ChannelState[channel].delay;
 		Set_VI_Control(pwl_delay_values,channel,old_val,&point_found,
-		               &range,&polarity,&entry,&word_out,&actual_pol);
+		               &range,&atten_range,&polarity,&entry,&word_out,&actual_pol);
 		break;
 	case pwl_period_values:
 		max_polarity=timing_polarities;
@@ -2920,7 +2959,7 @@ int Set_VI_Add_Cal(int parameter,int channel,float cal_point)
 		size_of_y_float=sizeof(globals.Flash.period_pwl_time);
 		old_val=1.0/globals.ChannelState[channel].frequency;
 		Set_VI_Control(pwl_period_values,channel,old_val,&point_found,
-		               &range,&polarity,&entry,&word_out,&actual_pol);
+		               &range,&atten_range,&polarity,&entry,&word_out,&actual_pol);
 		break;
 	case pwl_burst_values:
 		max_polarity=timing_polarities;
@@ -2931,7 +2970,7 @@ int Set_VI_Add_Cal(int parameter,int channel,float cal_point)
 		size_of_y_float=sizeof(globals.Flash.burst_pwl_time);
 		old_val=globals.ChannelState[channel].burst_time;
 		Set_VI_Control(pwl_burst_values,channel,old_val,&point_found,
-		               &range,&polarity,&entry,&word_out,&actual_pol);
+		               &range,&atten_range,&polarity,&entry,&word_out,&actual_pol);
 		break;
 	case pwl_rise_time_values:
 		max_polarity=ampl_polarities;
@@ -2942,7 +2981,7 @@ int Set_VI_Add_Cal(int parameter,int channel,float cal_point)
 		size_of_y_float=sizeof(globals.Flash.rise_time_pwl_time);
 		old_val=globals.ChannelState[channel].rise_time;
 		Set_VI_Control(pwl_rise_time_values,channel,old_val,&point_found,
-		               &range,&polarity,&entry,&word_out,&actual_pol);
+		               &range,&atten_range,&polarity,&entry,&word_out,&actual_pol);
 		break;
 	case pwl_slew_values:
 		max_polarity=timing_polarities;
@@ -2953,7 +2992,7 @@ int Set_VI_Add_Cal(int parameter,int channel,float cal_point)
 		size_of_y_float=sizeof(globals.Flash.slew_pwl_time);
 		old_val=globals.ChannelState[channel].slew;
 		Set_VI_Control(pwl_slew_values,channel,old_val,&point_found,
-		               &range,&polarity,&entry,&word_out,&actual_pol);
+		               &range,&atten_range,&polarity,&entry,&word_out,&actual_pol);
 		break;
 	case pwl_vcc1_values:
 		max_polarity=1;
@@ -2965,7 +3004,7 @@ int Set_VI_Add_Cal(int parameter,int channel,float cal_point)
 		size_of_y_float=sizeof(globals.Flash.vcc1_pwl_amp);
 		old_val=globals.ChannelState[true_channel].vcc1;
 		Set_VI_Control(pwl_vcc1_values,channel,old_val,&point_found,
-		               &range,&polarity,&entry,&word_out,&actual_pol);
+		               &range,&atten_range,&polarity,&entry,&word_out,&actual_pol);
 		break;
 	case pwl_vcc2_values:
 		max_polarity=1;
@@ -2977,7 +3016,7 @@ int Set_VI_Add_Cal(int parameter,int channel,float cal_point)
 		size_of_y_float=sizeof(globals.Flash.vcc2_pwl_amp);
 		old_val=globals.ChannelState[true_channel].vcc2;
 		Set_VI_Control(pwl_vcc2_values,channel,old_val,&point_found,
-		               &range,&polarity,&entry,&word_out,&actual_pol);
+		               &range,&atten_range,&polarity,&entry,&word_out,&actual_pol);
 		break;
 	case pwl_load_type_values:
 		max_polarity=load_type_polarities;
@@ -2988,7 +3027,7 @@ int Set_VI_Add_Cal(int parameter,int channel,float cal_point)
 		size_of_y_float=sizeof(globals.Flash.load_type_pwl_time);
 		old_val=globals.ChannelState[channel].load_type;
 		Set_VI_Control(pwl_load_type_values,channel,old_val,&point_found,
-		               &range,&polarity,&entry,&word_out,&actual_pol);
+		               &range,&atten_range,&polarity,&entry,&word_out,&actual_pol);
 		break;
 
 	}
@@ -3434,7 +3473,7 @@ int Set_Burst_Count(int channel,int count,float new_burst_time)
 int Set_Burst_Time(int check_possible_only,int word_override,int range_override,int channel,float new_burst_time)
 {
 	int count_word_out;
-	int point_found,relay_range,UseNegData,entry,actual_pol,word_out;
+	int point_found,relay_range,UseNegData,entry,actual_pol,word_out,dummy;
 
 	if (globals.Flash.max_burst_count[channel]<=1) {
 		return Unrecognized;
@@ -3467,7 +3506,7 @@ int Set_Burst_Time(int check_possible_only,int word_override,int range_override,
 	} else {
 		int status;
 		if ((status=Set_VI_Control(pwl_burst_values,channel,new_burst_time,&point_found,
-		                           &relay_range,&UseNegData,&entry,&word_out,&actual_pol))) {
+		                           &relay_range,&dummy,&UseNegData,&entry,&word_out,&actual_pol))) {
 			return status;
 		}
 	}
@@ -3525,7 +3564,7 @@ int Set_Burst_Time(int check_possible_only,int word_override,int range_override,
 
 int Set_rise_time(int check_possible_only,int word_override,int range_override,int channel,float new_rise_time)
 {
-	int point_found,relay_range,UseNegData,entry,actual_pol,word_out;
+	int point_found,relay_range,UseNegData,entry,actual_pol,word_out,dummy;
 	char range_control;
 
 	if (globals.Flash.fixed_rise_time[channel]) {
@@ -3556,7 +3595,7 @@ int Set_rise_time(int check_possible_only,int word_override,int range_override,i
 	} else {
 		int status;
 		if ((status=Set_VI_Control(pwl_rise_time_values,channel,new_rise_time,&point_found,
-		                           &relay_range,&UseNegData,&entry,&word_out,&actual_pol))) {
+		                           &relay_range,&dummy,&UseNegData,&entry,&word_out,&actual_pol))) {
 			return status;
 		}
 	}
@@ -3700,7 +3739,7 @@ int Set_current_limit(int check_possible_only,int channel,float new_adj_current_
 
 int Set_avrq_res(int check_possible_only,int word_override,int range_override,int channel,float new_res)
 {
-	int point_found,relay_range,UseNegData,entry,actual_pol,word_out;
+	int point_found,relay_range,UseNegData,entry,actual_pol,word_out,dummy;
 
 	if (!globals.Flash.switchable_load[channel]) {
 		return Unrecognized;
@@ -3742,7 +3781,7 @@ int Set_avrq_res(int check_possible_only,int word_override,int range_override,in
 
 		int status;
 		if ((status=Set_VI_Control(pwl_load_type_values,channel,compensated_new_res,&point_found,
-		                           &relay_range,&UseNegData,&entry,&word_out,&actual_pol))) {
+		                           &relay_range,&dummy,&UseNegData,&entry,&word_out,&actual_pol))) {
 			return status;
 		}
 	}
@@ -3775,7 +3814,7 @@ int Set_avrq_res(int check_possible_only,int word_override,int range_override,in
 int Set_slew(int check_possible_only,int word_override,int range_override,int channel,float new_slew)
 {
 	int check_valid;
-	int status,point_found,relay_range,UseNegData,entry,actual_pol,word_out;
+	int status,point_found,relay_range,UseNegData,entry,actual_pol,word_out,dummy;
 	char range_control;
 
 	if (!globals.Flash.curr_slew[channel]) {
@@ -3805,7 +3844,7 @@ int Set_slew(int check_possible_only,int word_override,int range_override,int ch
 		relay_range=range_override;
 	} else {
 		if ((status=Set_VI_Control(pwl_slew_values,channel,new_slew,&point_found,
-		                           &relay_range,&UseNegData,&entry,&word_out,&actual_pol))) {
+		                           &relay_range,&dummy,&UseNegData,&entry,&word_out,&actual_pol))) {
 			return status;
 		}
 	}
@@ -3852,7 +3891,7 @@ int Set_slew(int check_possible_only,int word_override,int range_override,int ch
 int Set_avrq_ampl(int check_possible_only,int word_override,int range_override,int channel,float new_avrq_ampl)
 {
 	int check_valid;
-	int status,point_found,relay_range,UseNegData,entry,actual_pol,word_out;
+	int status,point_found,relay_range,UseNegData,entry,actual_pol,word_out,dummy;
 	int true_channel;
 	int use_pwl;
 
@@ -3923,7 +3962,7 @@ int Set_avrq_ampl(int check_possible_only,int word_override,int range_override,i
 		}
 
 		if (use_pwl != pwl_vlogic_values)
-			if ((status=Set_VI_Control(use_pwl,channel,new_avrq_ampl,&point_found,&relay_range,&UseNegData,&entry,&word_out,&actual_pol))) {
+			if ((status=Set_VI_Control(use_pwl,channel,new_avrq_ampl,&point_found,&relay_range,&dummy,&UseNegData,&entry,&word_out,&actual_pol))) {
 				return status;
 			}
 
diff --git a/device-functions.h b/device-functions.h
index dc14abd..5199443 100644
--- a/device-functions.h
+++ b/device-functions.h
@@ -45,7 +45,7 @@ int Set_Dly_Shr_Cal(int channel,int calibration_point_number,float cal_point);
 int Set_Cal_Nom(int channel,int calibration_point_number,int parameter, float *nom_val);
 int Set_VI_Cal_Pnt(int parameter,int channel,int calibration_point_number,float cal_point);
 int Set_VI_Del_Cal(int parameter,int channel,int calibration_point_number);
-int Set_VI_Control(int parameter,int channel,float new_ampl,int *point_found,int *relay_range,
+int Set_VI_Control(int parameter,int channel,float new_ampl,int *point_found,int *relay_range,int *atten_range,
                    int *UseNegData,int *entry,int *word_out,int *actual_pol);
 int Set_VI_Add_Cal(int parameter,int channel,float cal_point);
 int Get_VI_Num_Pnts(int parameter,int channel);
diff --git a/globals.h b/globals.h
index 52cf1fc..cfc17b5 100644
--- a/globals.h
+++ b/globals.h
@@ -702,6 +702,10 @@ typedef struct {
 
 	float attenuators[max_channels][max_attens];			// addr 10070
 									// smallest attenuators first
+									// value = magnitude of attenuation.
+									// for example, for 20 dB, use 10.0
+									//              for 15 dB, use 5.62
+									//		for 10 dB, use 3.16
 
 	char spare_end;
 
diff --git a/monitor.c b/monitor.c
index 7c50922..44751e2 100644
--- a/monitor.c
+++ b/monitor.c
@@ -157,7 +157,7 @@ int I2C_Check_Monitors(void)
 	int monitor_word;
 	float step_size;
 	int channel;
-	int ampl_range,point_found,UseNegData,entry,word_out;
+	int ampl_range,point_found,UseNegData,entry,word_out,atten_range;
 
 	int update_display;
 	int use_neg_data;
@@ -195,7 +195,7 @@ int I2C_Check_Monitors(void)
 
 		/* determine current ampl_range */
 		Set_VI_Control(pwl_ampl_values,channel,globals.ChannelState[channel].amplitude,&point_found,
-		               &ampl_range,&UseNegData,&entry,&word_out,&actual_pol);
+		               &ampl_range,&atten_range,&UseNegData,&entry,&word_out,&actual_pol);
 
 		/* 5.0V is the full-scale voltage of the 12bit ADC */
 		globals.ChannelState[channel].Curr_Mon_value=((((float) monitor_word)/4095.0) * 5.0)