Hi Diego
1. Not sure if the question is related to NE64 but if it is I assume difference is between 16 bit timer and Period Interrupt Timer. In this case the PIT is designed to give a periodic interrupt and has no frills (the 16 bit timer can be used for a number of jobs such as counting extrernal pulses, generating waveforms and of course generating a simple periodic interrupt like the PIT - this can however be considered as under use of 16 bit timer when a PIT is otherwise available). I believe however that the PIT in the NE64 can not generate longer delays than 40ms when running from a 25MHz oscillator.
2. If the questions are related to above timers, when interrupts are disabled during several TICK, only one interrupt will be counted so time is lost.
3. These are my figures for the NE64 using a 16 bit timer and 25MHz oscillator and various prescaler set ups (from the uTasker project)
LOW_RES_MS - Clock with prescale 128 = about 0.16% accurate ms values, 2.5us resolution and limit of about 168ms max.
MED_RES_MS - Clock with prescale 32 = about 0.01% accurate ms values, 0.64us resolution and limit of about 42ms max.
HIGH_RES_MS - Clock with prescale 4 = about 0% accurate ms values, 0,16us resolution and limit of about 10.5ms max.
With prescaler 4 it is possible to generate ms delay with perfect accuracy by using a match value of 6250. However don't forget that if an interrupt routine handles this it may well have an extra response time of several % of the accuracy value until it used the TICK - and more if it has to wait for code which is blocking interrupts.
Regards
Mark
PS. Did you finally get the NE64 BDM working?
www.uTasker.com