i.MX287:cpu address is overlapped between On-chip ram and peripheral

cancel
Showing results for 
Search instead for 
Did you mean: 

i.MX287:cpu address is overlapped between On-chip ram and peripheral

292 Views
hwo
Contributor III

Hi all,

       Recent days, I come across a situation: there's a decoder, such as SN74LVC138APWR(3-input, 8-output), which uses cpu address pins(A6, A5, A4) as the input signals and LCD_RD_E(LCD pin) as cs signal. Doesn't have any LCD devices on the board. So the question is how can I obtain one of the eight output of decoder.

My thought is activating the LCD_RD_E pin, then write data to the A6A5A4 address and leave all the other cpu address pins to ZERO. However this address must be overlapped with on-chip ram.

So is it right to have the decoder connected like this or how can I arrange the address?

Thanks in advance!

Labels (2)
Tags (2)
0 Kudos
3 Replies

132 Views
igorpadykov
NXP TechSupport
NXP TechSupport

Hi h

if you are speaking about EMI_A00...pins then

address of External Memory EMI is 0x40000000 according to

Table 4-1. Address Map for i.MX28 i.MX28 Reference Manual (rev.1, 9/2010)

http://cache.freescale.com/files/dsp/doc/ref_manual/MCIMX28RM.pdf

Addresses of other modules also are shown on that table.

One can put data on decoder using processor pins as GPIOs, check Chapter 9 RM.

Best regards

igor

-----------------------------------------------------------------------------------------------------------------------

Note: If this post answers your question, please click the Correct Answer button. Thank you!

-----------------------------------------------------------------------------------------------------------------------

0 Kudos

132 Views
hwo
Contributor III

Thank you igor.

It's better to use GPIO as the input pins of decoder.

  I am a little confused about the cpu pins. According to the iMX28RM.pdf, I don't see the cpu address pins except some named by functional name such as EMI pins, LCD pins, etc.

So I want to know is it possible to have cpu address pins as the input of decoder. And where's the cpu address pins?

Thank you again!

0 Kudos

131 Views
igorpadykov
NXP TechSupport
NXP TechSupport

pelase read Chapter 9 Pin Control and GPIO (PinCtrl) iMX28RM.pdf,

in description you can find address.

~igor

0 Kudos