Maxim Integrated MAXQ Family - Manual (Page 90)

9-12
MAXQ Family User’s Guide
9.3.3 Measure Period
To measure the period of the signal seen on the T2P input pin, Timer 2 could be configured for a single-shot capture, no gating, either
edge (selected by the CCF[1:0] bits). The CPRL2 bit could be set to generate a reload on each capture edge.
; ------------------ Reset State: T2R = T2V = T2C = 0000h ------------------------
MOVE T2CFG, #00000100b ; T2CI =0 (sysclk/N input)
; T2DIV[2:0] =000 (/1)
; T2MD =0 (16-bit)
; CCF[1:0] =10 (falling edge)
; C/T2 =0 (timer/capture)
MOVE T2CNA, #10000110b ; ET2 =1 (enable Timer 2 ints)
; T2OE[0] =0 (input)
; T2POL[0] =0 (gating level = ‘0’)
; TR2L:TR2 =00 (don’t start timer 2)
; CPRL2 =1 (reload on capture edge)
; SS2 =1 (single-shot mode)
; G2EN =0 (gating disabled)
; ------------------ TCC2 Interrupt : PERIOD = T2C
T2P PIN
CODE EXECUTION:
POINT A
CODE EXECUTION:
POINT B
1A 2A
1B 2B
EVENTS:
1A: FALLING EDGE CAUSES CAPTURE/RELOAD; SINGLE-SHOT CAPTURE CYCLE BEGINS.
2A: FALLING EDGE CAUSES CAPTURE/RELOAD; SINGLE-SHOT CAPTURE CYCLE ENDS; PERIOD = T2C.
1B AND 2B: SAME SEQUENCE AS 1A–2A, EXCEPT THAT THE SINGLE-SHOT CAPTURE CYCLE DOES NOT BEGIN UNTIL THE FIRST FALLING EDGE IS DETECTED.
Figure 9-6. Timer 2 Application Example—Measure Period
Maxim Integrated