topic Re: K20 based MK20FN1M0VMD12 PORT flexbus control drive strength question in Kinetis Microcontrollers

K20 based MK20FN1M0VMD12 PORT flexbus control drive strength question

sherry_zahid — Thu, 05 Nov 2015 14:01:35 GMT

Hi,

I am using a K20 based MK20FN1M0VMD12

I am using the flexbus to connect to an SRAM chip. I am using the following pins for control signals to the SRAM

Pin name	ALT Mode	Function
PTD1	ALT 5	FB_CS0_B
PTC11	ALT 5	FB_RW_B
PTB19	ALT 5	FB_OE_B
PTC17	ALT 5	FB_BE31_24_B
PTC16	ALT 5	FB_BE23_16_B

I am using these pins in the ALT 5 mode, I need to have high drive strength on these control signals.

I found in the datasheet that bit 5 of the pin control registers need to be set to 1 for high drive strength.

PORTx_PCRy[n]
x = port letter
y = pin number
n = register bit#

My question is, although I am operating in ALT 5 mode for these pins, can I still enable high drive strength on these pins by setting the corresponding (bit 6) PCR bits? i.e.

FB_CS0_B	PORTD_PCR1[6] = 1
FB_RW_B	PORTC_PCR11[6] = 1
FB_OE_B	PORTB_PCR19[6] = 1
FB_BE31_24_B	PORTC_PCR17[6] = 1
FB_BE23_16_B	PORTC_PCR16[6] = 1

Will these pins have high drive strength if I set bit 6 of these registers to high(1)? (I am using ALT5 function of these pins for flexbus SRAM control signals)

Thank you for your time.

Re: K20 based MK20FN1M0VMD12 PORT flexbus control drive strength question

jeremyzhou — Fri, 06 Nov 2015 02:32:29 GMT

Hi Sherry,

It's ok to set the bit 6 to 1 when pin work in the ALT5 mode.

The Driver Strength Enable (DSE) is valid in all digital pin muxing modes, definitely contains the ALT5.

Hope it helps.
Have a great day,
Ping

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Re: K20 based MK20FN1M0VMD12 PORT flexbus control drive strength question

sherry_zahid — Fri, 06 Nov 2015 13:22:05 GMT

Thanks Jeremyzhou,

That answers my question perfectly.