Rabbit 2000™ Microprocessor - UTN

10.1.1 Hardware ChangesOrdinarily, CS0/OE0/WE0 of the Rabbit processor are connected to a flash chip, andCS1/OE1/WE1 are connected to RAM. However, if only RAM is to be used, CS0/OE0/WE0 mustbe connected the RAM. This is because on power up or reset, the Rabbit will begin fetchinginstructions from whatever is hooked up to CS0/OE0/WE0.10.1.2 Software ChangesIn order to program a RAM only board from Dynamic C or the Rabbit Field Utility (RFU), severalchanges are needed. When Dynamic C or the RFU first start, they put the Rabbit based targetboard in bootstrap mode where it awaits data sent via “triplets.” These programs then send tripletsthat map the lowest quadrant of physical memory to CS1/OE1/WE1 in order to load a primaryloader to RAM. The first set of triplets loaded to the target is contained in a file called coldload.bin.A different coldload.bin is required in order to map the lowest memory quadrant toCS0/OE0/WE0. The image file for this program is \BIOS\RAMONLYCOLDLOAD.BIN.Touseit,rename BIOS\COLDLOAD.BIN to BIOS\COLDLOAD.BAK, and rename \BIOS\RAMONLY-COLDLOAD.BIN to \BIOS\COLDLOAD.BIN. (Later versions of Dynamic C may have a GUImethod of choosing the cold loader.)The primary loader loads a secondary loader, which doesn’t affect the memory mapping. The secondaryloader loads the Rabbit BIOS to RAM (from the application program image file in the caseof the RFU, by compiling the BIOS straight to the target in the case of Dynamic C.) One of thefirst things the BIOS does in program mode is copy itself to flash, and then transfer execution tothe flash copy. When the board powers up later without the programming cable attached, it willstart running the BIOS in flash.The special BIOS file \BIOS\RAMONLYBIOS.C eliminates the self copy step and initializes theMIU/MMU correctly to match the hardware configuration. This BIOS can be selected as the userdefinedBIOS by using the Options | Compiler dialog box.52 Rabbit 2000 Microprocessor