/XCLKS 直接接地可以吗?

cancel
Showing results for 
Search instead for 
Did you mean: 

/XCLKS 直接接地可以吗?

Jump to solution
167 Views
nxpxhy13
Contributor I

/XCLKS直接接地,不用3.3k电阻,这样行不行?设计PCB的时候忽略了这个管脚

 

/ XCLKS direct ground, no 3.3k resistor, okay? This pin was ignored when designing the PCB.

0 Kudos
1 Solution
160 Views
lama
NXP TechSupport
NXP TechSupport

Hi

the pin is use to select oscillator configuration during reset.

(You do not mention the MCU number.)

For example, in the case of S12XEP100 (Table 1-10. Signal Properties Summary) the pin is pulled up during reset. In your configuration it will read log. level = 0 and the MCU sets oscilator configuration corresponding to this level.

 

After reset the pin is set as Hi-Z input pin because DDRE.7 = 0 (reset status)....chapter 2.3.12

If you set it as output port (DDRE.7 = 1) and you use it as ECLKX2output or you prite to the pin log.1 then it cause shortcut.

If it is grounded in your design you have to ensure the pin will newer be set as output pin with log.1 written to it.

 

So finally; the configuration is possible but unsafe.

 

Best regards,

Ladislav

 

 

View solution in original post

0 Kudos
1 Reply
161 Views
lama
NXP TechSupport
NXP TechSupport

Hi

the pin is use to select oscillator configuration during reset.

(You do not mention the MCU number.)

For example, in the case of S12XEP100 (Table 1-10. Signal Properties Summary) the pin is pulled up during reset. In your configuration it will read log. level = 0 and the MCU sets oscilator configuration corresponding to this level.

 

After reset the pin is set as Hi-Z input pin because DDRE.7 = 0 (reset status)....chapter 2.3.12

If you set it as output port (DDRE.7 = 1) and you use it as ECLKX2output or you prite to the pin log.1 then it cause shortcut.

If it is grounded in your design you have to ensure the pin will newer be set as output pin with log.1 written to it.

 

So finally; the configuration is possible but unsafe.

 

Best regards,

Ladislav

 

 

View solution in original post

0 Kudos