Motorola DSP56301 - Manual (Page 275)

Operating Modes
Triple Timer Module 9 -13
Figure 9-10. Event Counter Mode, TRM = 0
Mode 3 (internal clock): TRM = 0
N = write preload
M = write compare
TE
(TIO pin or prescale CLK)
TLR
TCPR
TCF (Compare Interrupt if TCIE = 1)
first event
M
N
if clock source is from TIO pin,
TIO < CPUCLK + 4
Clock
1 Counter (TCR) 0 N N + 1 M 0 M + 1
TOF (Overflow Interrupt if TCIE = 1)
NOTE: If INV = 1, counter is clocked on 1-to-0 clock transitions, instead of 0-to-1 transitions.