Slajd12 (174)

MC6840 TIMER COUNTER

TABLE 8 - FREOUENCY COMPARlSON MODĘ

Modę	Bit 3	Bit 4	Control Reg. Bit 5	Counter Initialization	Counter Enable Flip-Flop Set ICE)	Counter Enable Flip-Flop Reset łCEł	Interrupt Flag Set (I)
Freguency	1	0	0	G* *|« iCt+TOI+R	G l	W + R +1	G1 Bofore TO
Corrpanson	1	0	1	Gl.T+R	Gł •	W+R + l	TO Befcre Gi
Pulse Width	1	1	0	"5*1 • 1 + R	G1 W*R*I	W + R + l+G	Gt Before TO
Companson	1	1	1	G1 • + R	G • • W • R • 1	W + R 1 + G	TO Before (Tf

Gł = Negaiive trarsnion o‘ Gate mpu:

W =Write Timer Latches Command. _

R =Timer Reset (CR‘iO = I or £xi9rna! RESET = 01 N = 16-Bit Number in Counter Latch TO = Counter Time Out (Ali Zerc Condition)

I = Interrypt for a given timer.

'Ali time intervals shown above assume tbe Gate (G) and Clock iC) signals are sycnhronized to the system doi (Eł with the speofied setup and hołd time requ>rements