topic Can I make a 32-bit counter from FTM? in Kinetis Microcontrollers

Can I make a 32-bit counter from FTM?

michaelschwager — Fri, 07 Nov 2014 23:23:18 GMT

I'm using MK60DN512VLQ10 with MQX 4.1 on a custom PCB.

Currently I have FTM0 configured as a free-running counter from FTM_CLKIN1. I'm driving this with an external 100kHz clock.

However I'd like to have a 32-bit counter, preferably without software intervention, ie interrupts, etc.

I thought I could use FTM1 with prescaler = 65536, but the prescaler doesn't go that high. It only goes to 128.

Can I chain two FTMs together to create a 32-bit counter? The clock source of a given FTM doesn't appear to allow the MSB of a different FTM.

I also have the 100kHz clock going to FTM0_CH4 input, but I'm not using that for anything now.

thanks

Re: Can I make a 32-bit counter from FTM?

Hui_Ma — Tue, 11 Nov 2014 08:04:50 GMT

Hi Michael,

Unfortunately, Kinetis Flextimer doesn't support chained timer.

So, customer can not chain two Flextimer as a 32-bit counter.

Customer can consider to use PIT, which is a 32-bit timer and also could support chained timer for 64-bit timer.

Wish it helps.
best regards
Ma Hui

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Re: Can I make a 32-bit counter from FTM?

michaelschwager — Tue, 11 Nov 2014 19:57:09 GMT

Thanks, this is what I discovered.

I put an interrupt every time overflow flag (TOF) goes high, then increment my variable by 0x10000;

I need this to connect to an external clock from an FPGA (I’m synchronizing multiple boards to a global 100kHz clock), so I cannot use PIT, which states “The PIT module has no external pins”.