Rabbit 2000 Designers Handbook

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Rabbit 2000 Designers Handbook Manual pdf 29 page image

Designer’s Handbook 277. BIOS Support for Program CloningA program can be loaded into a controller by compiling it using Dynamic C. However,this is awkward and slow in some situations. If cloning is enabled in the BIOS, a Rabbit-based system can copy itself into another controller by connecting the programming portsof the two controllers together in the proper way as shown in Figure 6.Figure 6. Programming CableIf the cloning cable is connected to the master, the master detects this because the signalCLKA is held low. This is detected in the BIOS after the reset ends, and the cloning sup-port of the BIOS is then invoked. The cloning program cold-boots the target system byresetting it and downloading a primary boot program. The master then sends the entireBIOS over to the clone, where the boot program receives it and stores it in RAM (just likeDynamic C does when compiling the BIOS). A CRC check of the BIOS is performed onboth the master and clone, and the results are compared. The clone is reset again, and theBIOS begins running. Finally, the master sends blocks of data at high speed, and the dataare written to the flash memory. Data transfer can take place at 57,600 bps or 115,200 bps.When the entire flash contents (except for the system ID block) have been transferred, thetarget flashes the cable LED in a distinctive pattern to indicate that the programming isdone. At that point the cable can be unplugged and plugged into another target. When themaster is reset, it will program the next target.To enable cloning, two options must be set at the top of the BIOS. First,ENABLECLONING should be set to 1. If this is set, the BIOS will take up additional mem-ory because of the functions required for cloning. The cloning baud rate is set by settingCLONINGBAUDRATE to either 0 (57,600 bps) or 1 (115,200 bps).Once cloning is enabled, compile your program to flash, then detach the programmingcable and attach the cloning cable. Make sure the “master” end of the cable is connectedto the master controller (the cable is not reversible) and that pin 1 lines up correctly on Ω