External SRAM and Flexbus - Help Needed

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External SRAM and Flexbus - Help Needed

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Contributor V

Hi,

I've hooked up an external SRAM chip to the Flexbus of a Kinetis K66.

Having written a very basic application to test that the SRAM is working ok, I've since run into problems and I think it may be related to the wiring of my Flexbus signals through to the SRAM. Just for reference, I'm using a IS61WV102416BLL chip.

My Flexbus to SRAM pin mapping is as follows:

FB_AD[15:0] = SRAM_A[15:0]

FB_A[19:16] = SRAM_A[19:16]

FB_AD[31:16] = SRAM_D[15:0]

FB_CS0 = SRAM_CE

FB_OE = SRAM_OE

FB_RW = SRAM_WE

FB_LB = SRAM_LB

FB_HB = SRAM_HB

I'm using the following code to initialize the FB:

#define ADDR     0x90000000

// Address signals [19:0]

  PORTD_PCR6 = PORT_PCR_MUX(5); // FB.AD0

  PORTD_PCR5 = PORT_PCR_MUX(5); // FB.AD1

  PORTD_PCR4 = PORT_PCR_MUX(5); // FB.AD2

  PORTD_PCR3 = PORT_PCR_MUX(5); // FB.AD3

  PORTD_PCR2 = PORT_PCR_MUX(5); // FB.AD4

  PORTC_PCR10 = PORT_PCR_MUX(5); // FB.AD5

  PORTC_PCR9 = PORT_PCR_MUX(5); // FB.AD6

  PORTC_PCR8 = PORT_PCR_MUX(5); // FB.AD7

  PORTC_PCR7 = PORT_PCR_MUX(5); // FB.AD8

  PORTC_PCR6 = PORT_PCR_MUX(5); // FB.AD9

  PORTC_PCR5 = PORT_PCR_MUX(5); // FB.AD10

  PORTC_PCR4 = PORT_PCR_MUX(5); // FB.AD11

  PORTC_PCR2 = PORT_PCR_MUX(5); // FB.AD12

  PORTC_PCR1 = PORT_PCR_MUX(5); // FB.AD13

  PORTC_PCR0 = PORT_PCR_MUX(5); // FB.AD14

  PORTB_PCR18 = PORT_PCR_MUX(5); // FB.AD15

  PORTD_PCR8 = PORT_PCR_MUX(5); // FB.A16

  PORTD_PCR9 = PORT_PCR_MUX(5); // FB.A17

  PORTD_PCR10 = PORT_PCR_MUX(5); // FB.A18

  PORTD_PCR11 = PORT_PCR_MUX(5); // FB.A19

  // Data signals [15:0]

  PORTB_PCR17 = PORT_PCR_MUX(5); // FB.D0 [FB.AD16]

  PORTB_PCR16 = PORT_PCR_MUX(5); // FB.D1 [FB.AD17]

  PORTB_PCR11 = PORT_PCR_MUX(5); // FB.D2 [FB.AD18]

  PORTB_PCR10 = PORT_PCR_MUX(5); // FB.D3 [FB.AD19]

  PORTB_PCR9 = PORT_PCR_MUX(5); // FB.D4 [FB.AD20]

  PORTB_PCR8 = PORT_PCR_MUX(5); // FB.D5 [FB.AD21]

  PORTB_PCR7 = PORT_PCR_MUX(5); // FB.D6 [FB.AD22]

  PORTB_PCR6 = PORT_PCR_MUX(5); // FB.D7 [FB.AD23]

  PORTC_PCR15 = PORT_PCR_MUX(5); // FB.D8   [FB.AD24]

  PORTC_PCR14 = PORT_PCR_MUX(5); // FB.D9 [FB.AD25]

  PORTC_PCR13 = PORT_PCR_MUX(5); // FB.D10 [FB.AD26]

  PORTC_PCR12 = PORT_PCR_MUX(5); // FB.D11 [FB.AD27]

  PORTB_PCR23 = PORT_PCR_MUX(5); // FB.D12 [FB.AD28]

  PORTB_PCR22 = PORT_PCR_MUX(5); // FB.D13 [FB.AD29]

  PORTB_PCR21 = PORT_PCR_MUX(5); // FB.D14 [FB.AD30]

  PORTB_PCR20 = PORT_PCR_MUX(5); // FB.D15 [FB.AD31]

  // Byte control signals [HB:LB]

  PORTC_PCR18 = PORT_PCR_MUX(5); // FB.BE15_8

  PORTC_PCR17 = PORT_PCR_MUX(5); // FB.BE7_0

  // Chip select signal

  PORTD_PCR1 = PORT_PCR_MUX(5); // FB.CS0#

  // Read/Write signal

  PORTC_PCR11 = PORT_PCR_MUX(5); // FB.RW#

  // Output enable signal

  PORTB_PCR19 = PORT_PCR_MUX(5); // FB.OE#

  SIM_SOPT2 |= SIM_SOPT2_FBSL(3);

  SIM_SCGC7 |= SIM_SCGC7_FLEXBUS_MASK;

  FB_CSAR0 = ADDR;

  // 16bit data port size

  // Auto-acknowledge

  // Some wait states

  // Byte-enable mode so BE is asserted for read and write

  FB_CSCR0 = FB_CSCR_PS(2) | FB_CSCR_AA_MASK | FB_CSCR_WS(5) | FB_CSCR_BEM_MASK;

  FB_CSMR0 = FB_CSMR_V_MASK | FB_CSMR_BAM(0x7);

  // Enable FB_BE_15_8 and FB_BE_7_0

  FB_CSPMCR = FB_CSPMCR_GROUP4(2) | FB_CSPMCR_GROUP5(2);

With the following code used to write/read back data from the SRAM:

  *((uint8_t *)ADDR + 1) = 0x05;

  *((uint8_t *)ADDR + 2) = 0x04;

  *((uint8_t *)ADDR + 3) = 0x03;

  *((uint8_t *)ADDR + 4) = 0x02;

  *((uint8_t *)ADDR + 5) = 0x01;

  f = *((uint8_t *)ADDR + 1);

  printf("%x", f);

  f = *((uint8_t *)ADDR + 2);

  printf("%x", f);

  f = *((uint8_t *)ADDR + 3);

  printf("%x", f);

  f = *((uint8_t *)ADDR + 4);

  printf("%x", f);

  f = *((uint8_t *)ADDR + 5);

  printf("%x", f);

The result of printf either comes out as a "90" or a "00" which is coincidental, based on the ADDR value.

I'm not convinced the wiring of the Flexbus is entirely correct but equally, I'm sure I'm missing something in the initialization.

Any advice would be greatly appreciated.

Kev

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Contributor V

Ok, so having a weekend off has clearly helped - the SRAM access now works as expected.

The only thing I needed to change from my initial setup was to swap the HB/LB signals from PORTC[18] and [19] to PORTC[17] and [18] respectively, due to the fact that BLS=0.

This post proved most useful:

https://community.freescale.com/message/322857

View solution in original post

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Contributor IV
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Contributor V

Ok, so having a weekend off has clearly helped - the SRAM access now works as expected.

The only thing I needed to change from my initial setup was to swap the HB/LB signals from PORTC[18] and [19] to PORTC[17] and [18] respectively, due to the fact that BLS=0.

This post proved most useful:

https://community.freescale.com/message/322857

View solution in original post

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NXP Employee
NXP Employee

Hi Kev,

Please review following link to see if it helps.

Flexbus in MQX

Regards,

David

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Contributor V

Hi David,

Thanks for the link.

Unfortunately, the scope of the document isn't sufficient for me to see whether my Flexbus is set up correctly. I've used the Flexbus on an LCD display before and had no issue - it works perfectly - I just can't decide whether its a hardware issue on my board due to the signals being mapped incorrectly (the upper address bits) or a software initialization/configuration issue.

Kind regards,

Kevin

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Contributor V

Ok, so I guess a couple of things I've noticed following this post:

https://community.freescale.com/thread/309447

My pin mux-ing for the upper 4 address signals was incorrect - I specified PORT_PCR_MUX(5) but it should have been PORT_PCR_MUX(6). Also, it would appear that because my data is not byte-lane shifted (BLS = 0) and resides on FB_AD[31:16] that I should be using BE_31_24 and BE_23_16 rather than BE_15_8 and BE_7_0.

I've changed the former, which made no difference. I'm hoping that the latter will do it!

Can anyone offer any advice on the above?

Kind regards,

Kevin

UPDATE

I'm now more confused. The SRAM_HB and SRAM_LB signals are routed through to PORTC_18 and PORTC_19 respectively. In the reference manual, these signals (for pin mux 5) are descried as FB_BE15_8_BLS23_16_b and FB_BE7_0_BLS31_24_b. Does this now mean that I am actually using the correct ones??

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