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RCM6700 io bus usage

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is there any dynamic c example code for using the external io bus (address, data, iord, iowr, chip selects), making use of some of the hardware support described in the Rabbit 6000 CPU manual section 31?

or should i just bit-bang it?

i need to talk to some legacy hardware, including a uart and an 8255 digital io chip.

asked Nov 10, 2017 in Rabbit Software by ebio New to the Community (0 points)

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1 Answer

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The external I/O bus works well on the RCM6700. Dynamic C 10.72C includes some updated samples to interface with an LCD/Keypad module that originally shipped for the RCM3000 development hardware.

I suggest taking a look at the schematic for the LCD/Keypad (https://www.digi.com/products/models/20-101-0502) and the RCM3000 prototyping board (http://ftp1.digi.com/support/documentation/0900137_e.pdf) to understand the connections.

Then look at Samples/RCM6700/LCD_Keypad/LCDKEYFUN.C to see which I/O lines are used from the RCM6700:

"Bridge the following pins on the two boards: PA0 to PA7, PB2 to PB5, PE3*, PE6, /IORD, /RESET and GND. *Simply grounding PE3 on the RCM3000 prototyping board will also work."

And then you'll unfortunately have to dig through multiple libraries looking at code related to this feature.

Samples/Libraries/RCM67xx.LIB shows the configuration registers used by Displays/LCD122KEY7.LIB to configure the board for external I/O. You can also look at the USE_DISPLAY_KEYPAD code changes in brdInit() to understand some of the setup requirements.

I'm sorry there isn't a self-contained sample for an interface to an octal latch and buffer to demonstrate reading and writing with the external I/O bus. Hopefully the resources listed will be enough to get started with the feature in your project.
answered Nov 10, 2017 by TomCollins Veteran of the Digi Community (2,382 points)