: $Id: fzap.mod,v 1.1 2009/04/21 19:17:15 hines Exp hines $ COMMENT fzap.mod A bogus point process that contains the variable x, which oscillates starting at t = del >= 0. The frequency f of the oscillation increases linearly with time from f0 at t == del to f1 at t == del + dur, where both del and dur are > 0. fzap uses the event delivery system to ensure compatibility with adaptive integration. ================= NOTES AND CAVEATS ================= 1. If x were a RANGE variable, an assignment statement would have to be inserted into proc advance() in order for the value of x to be used by other mechanisms--e.g. proc advance() { is_xtra = Fzap[0].x fadvance() } However, that would be incompatible with adaptive integration. To eliminate the need for such an assignment statement, x is a POINTER. This preserves compatibility with adaptive integration. 2. On every fadvance, the statements that evaluate Fzap's x should be executed before the statements in any client mechanism that relies on the value of Fzap's x. To that end, the value of x is computed in a BEFORE BREAKPOINT block, which will take care of any client mechanism that uses Fzap's x in a BREAKPOINT block. However, some client mechanisms may have their own BEFORE BREAKPOINT blocks that need the value of Fzap's x. xtra is such a mechanism. In this situation, care is required to ensure that the statements in Fzap's BEFORE BREAKPOINT block are executed first. This can be done by compiling the mod file that defines Fzap _before_ the client mechanism's mod file. There are two ways to make this happen: A. Invoke nrnivmodl with a command line that presents the file names in the desired sequence. UNIX/Linux users may be quite comfortable with this. B. Choose mod file names so that Fzap's mod file appears before the name of any client mod files in an alphabetical listing. For the example of Fzap and xtra, the file names fzap.mod and xtra.mod would be quite suitable. This is more convenient for users of all operating systems, but especially MSWin and OS X, whose users are accustomed to compiling all mod files in a directory with mknrndll or "drag and drop," respectively. 12/11/2008 NTC ENDCOMMENT NEURON { POINT_PROCESS Fzap RANGE del, dur, f0, f1, amp, f POINTER x } UNITS { PI = (pi) (1) } PARAMETER { del (ms) dur (ms) f0 (1/s) : frequency is in Hz f1 (1/s) amp (1) } ASSIGNED { f (1/s) x (1) on (1) } INITIAL { f = 0 x = 0 on = 0 if (del<0) { del=0 } if (dur<0) { dur=0 } if (f0<=0) { f0=0 (1/s) } if (f1<=0) { f1=0 (1/s) } : do nothing if dur == 0 if (dur>0) { net_send(del, 1) : to turn it on and start frequency ramp net_send(del+dur, 1) : to stop frequency ramp, freezing frequency at f1 } } COMMENT The angular velocity in radians/sec is w = 2*PI*f, where f is the instantaneous frequency in Hz. Assume for the moment that the frequency ramp starts at t = 0. f = f0 + (f1 - f0)*t/dur Then the angular displacement is theta = 2*PI * ( f0*t + (f1 - f0)*(t^2)/(2*dur) ) = 2*PI * t * (f0 + (f1 - f0)*t/(2*dur)) But the ramp starts at t = del, so just substitute t-del for every occurrence of t in the formula for theta. ENDCOMMENT BEFORE BREAKPOINT { if (on==0) { f = 0 x = 0 } else { f = f0 + (f1 - f0)*(t-del)/dur x = amp * sin( 2*PI * (t-del) * (f0 + (f1 - f0)*(t-del)/(2*dur)) * (0.001) ) } } NET_RECEIVE (w) { : respond only to self-events with flag > 0 if (flag == 1) { VERBATIM on = (double)(on == 0.0); ENDVERBATIM } }