I have a project that requires synchronizing the Arduino mega1280 clock with the sample clocks of 2 other chips. I'd like to use the ATmega1280 CLKO buffer on pin 9 of the chip. It does not appear to be broken out to any pin or pad. Was there a design reason for this? What I need to know, is it safe(will it mess with any library functions) to solder a jumper from my 2 external chips CLKIN to pin 9 of the ATmega1280, set the CKOUT fuse, and disable the prescaler(with JTAGICE mkII). Is there a safer method to get the same results without hand soldering the chiplead?
From the chip datasheet;
"10.10 Clock Output Buffer
The device can output the system clock on the CLKO pin. To enable the output, the CKOUT
Fuse has to be programmed. This mode is suitable when the chip clock is used to drive other cir-
cuits on the system. The clock also will be output during reset, and the normal operation of I/O
pin will be overridden when the fuse is programmed. Any clock source, including the internal RC
Oscillator, can be selected when the clock is output on CLKO. If the System Clock Prescaler is
used, it is the divided system clock that is output. "
What is the default setting of the prescaler? What libraries and functions would be affected if I changed the prescaler?
Those 2 external chips use an 8bit multiplexed address/data bus. I want to use the XMEM bus on Arduino pins 22-29, ALE on pin 39, /RD on pin 40, /WR on pin 41. Is there a library already written to do this? I need any example code available for managing the CS lines and address space when connecting the bus to 2 Mektronix MCT-1200 chips and an HD44780 character LCD. If I use the LiquidCrystal library in 8 bit mode and initialize it with the XMEM pins will that screw with the other devices on the bus? Do I have to write my own LCD library to use on the bus?
Thanks for any guidance, I will post any results that work.