[Simh] Device Timing Question

[Mark Pizzolato - Info Comm]

Hi Rob,

Simh device wait units are instructions.

Usually a device has no specific knowledge about the significance of wall time vs instructions.  To help solve this problem some methods exist to specify wait times which correlate with the simulated machine's clock ticks which are dynamically calibrated to produce a number of instructions per unit of time (clock tick).  Devices usually behave well if wait units are aligned on clock ticks and doing this helps produce better 'idling' behavior.  A device which wants to wake up on every simulated clock tick would code the following:

extern int32 tmxr_poll;                                 /* calibrated delay */



    sim_activate (uptr, clk_cosched (tmxr_poll));       /* reactivate */

Good Luck,


-        Mark

From: simh-bounces at trailing-edge.com [mailto:simh-bounces at trailing-edge.com] On Behalf Of Rob Jarratt
Sent: Sunday, October 07, 2012 10:05 AM
To: simh at trailing-edge.com
Subject: [Simh] Device Timing Question


The device I am emulating appears to be running too fast for the driver that uses it and I need to get to grips with device timing in SIMH. I have never fully understood the use of sim_activate, in particular what are the units of time that are passed to this routine?

Thanks

Rob
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