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AURIX™ Forum Discussions

User17142
Level 1
Level 1
Hi,

I am trying to execute sample program from the vendor for driving external eeprom (25LC640A) using tc234 QSPI0. The below parameters are configured as follows:

BACON.LPRE = 1
BACON.LEAD = 3

fBaud = 200/((49+1)*(1+1+1+1)) = 1 MHz

when I am using the formula as given in user manual TLEAD = TBAUD2 * 4^LPRE * (LEAD+1) I am getting TLEAD as 80 us (10^-6 * 4^4 * 5) but when I measured through oscilloscope I am getting the TLEAD as 2.56 us (approx.). Could you please let me know what I am doing wrong? I believe I am missing something in the calculation.

Thanks for your time.

Many Thanks,
Kumaresh
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8 Replies
cwunder
Employee
Employee
25 likes received 25 solutions authored 100 sign-ins
Assuming 200MHz (fBAUD2), I calculate 80 nsec not 80 usec. You should also check the output driver strength for SPI0 pins are set to speed grade 1.
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User17142
Level 1
Level 1
Hi,

I checked the output driver strength and it set to 1. I believe I am confused with the calculation. Could you please elaborate on how you arrived at 80 ns. Thanks for your time.

Regards,
Kumaresh
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cwunder
Employee
Employee
25 likes received 25 solutions authored 100 sign-ins
From the User’s Manual
TLEAD = TBAUD2 * BACON.LPRE * BACON.LEAD

For the calculation of the delay:
TBAUD2 = 1 / fBAUD2
TLEAD = TBAUD2 * 4^LPRE * (LEAD+1)

You provided the following parameters
BACON.LPRE = 1
BACON.LEAD = 3
fBAUD2 = 200MHz

Therefore:
TBAUD2 = 1/200MHz = 5e-9 or 5nsec
LPRE = 4^1 = 4
LEAD = 3 + 1 = 4
The value of the LEAD delay is 5e-9 * 4 * 4 = 80e-9 or 80nsec
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User17142
Level 1
Level 1
Thanks for your detailed reply. I believe I have misunderstanding in substituting the values in BACON.LPRE * BACON.LEAD. As per the manual from my understanding when LPRE = 001b I need to use 4 and TPRE = 3 I need to plug in 4 (pg no 1841 Basic Configuration Register Table). So I plugged in the values as 5e-9 * 4^4 * (4 + 1) and calculated the value as 640 microsec. Could you please comment on how to infer the values from the attached image? In other words my query is what does the value of 0D means in LEAD. Thanks for your time.
3703.attach
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cwunder
Employee
Employee
25 likes received 25 solutions authored 100 sign-ins
The Formula:

3706.attach

This what you asked:
BACON.LPRE = 1
BACON.LEAD = 3







Now you ask
Could you please comment on how to infer the values from the attached image? In other words my query is what does the value of 0D means in LEAD






See the calculation of the LEAD delay above.

If the LEAD is 0 decimal, then this what is used in the formula (i.e. LEAD + 1 which is 0 + 1) while the BACON.LEAD = 0 is the register value
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User17142
Level 1
Level 1
Thanks Chris for the detailed clarification. It gave me more clearer inference.
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User14049
Level 3
Level 3
cwunder wrote:
From the User’s Manual
TLEAD = TBAUD2 * BACON.LPRE * BACON.LEAD

For the calculation of the delay:
TBAUD2 = 1 / fBAUD2
TLEAD = TBAUD2 * 4^LPRE * (LEAD+1)

You provided the following parameters
BACON.LPRE = 1
BACON.LEAD = 3
fBAUD2 = 200MHz

Therefore:
TBAUD2 = 1/200MHz = 5e-9 or 5nsec
LPRE = 4^1 = 4
LEAD = 3 + 1 = 4
The value of the LEAD delay is 5e-9 * 4 * 4 = 80e-9 or 80nsec


Hi,

Can you help me to know fBAUD2 is SPI operating frequency or aurix operating frequency.
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cwunder
Employee
Employee
25 likes received 25 solutions authored 100 sign-ins
For the TC2xx devices the fBAUD2 is derived from either the fPLL or fBACK and you can also divide it. It depends on the settings in the CCUCON0 register.
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