This directory contains the source code for the binary files found in BIOS/. Use build.bat to compile a single file at a time. If you have Borland MAKE Version 5.2 installed, the Makefile should work for building and installing all binary files.

The following attempts to document the "cold boot" sequence Dynamic C 10 (DC) and the Rabbit Field Utility (RFU) use on Rabbit 4000, 5000 and 6000 boards. Read the processor documentation for details on bootstrapping from serial port A.

DC and RFU reset the processor with the following sequence:

1. Set pins SMODE1=1 and SMODE0=1 to enable asynchronous serial bootstrapping at 2400 baud.
2. Hold /RESET low (via DTR pin of serial connection) for 500ms.
3. Set /RESET high and wait another 500ms.
4. Send a triplet to set GOCR=0x30, pulling STATUS high.

The compiler and RFU monitor the processor's STATUS line via the DSR pin of the serial connection, and use small programs to discover target capabilities and toggle the STATUS pin in response. Each detection routine typically starts by setting GOCR = 0x20 and verifies that STATUS goes low, then checks whether STATUS goes high.

1. If processor verification is turned on, make sure a Rabbit is connected to the programming cable, using the following sequence (sent as triplets: 0x80, the register address, and the register value):
   • WDTTR = 0x51
   • WDTTR = 0x54
   • GOCR = 0x30 (expect STATUS to be high)
   • GOCR = 0x20 (expect STATUS to be low)
2. Probe for internal RAM on /CS3 by setting MB0CR to 0x43, then loading a small program at address 0 (ld a, 0x30; ioi ld (GOCR), a; jr -2) and starting it. If STATUS goes low, the board has RAM on /CS3 and is either a Rabbit 5000 or Rabbit 6000. Note that including Detect Internal Memory=0 in the project file will skip this step and force the use of RAM on /CS1 for bootstrapping.
3. On a Rabbit 4000, detect memory type (either 8-bit or 16-bit) using precoldload.bin. DC/RFU skips this step on Rabbit 5000/6000 since it will use the internal RAM with an 8-bit interface.
4. Detect flash type using checkRamCS0.bin. A Rabbit 4000 with 16-bit memory skips this step and assumes parallel flash. Other boards configure MB2CR for CS0/OE0 which will map either parallel flash or RAM to that quadrant. (Note that DC/RFU no longer make use of checkCS04mem.bin.)

After identifying characteristics of the hardware, DC/RFU sends the appropriate cold loader to the target (via triplets):

• Parallel flash (8-bit RAM): coldload.bin
• Parallel flash (16-bit RAM): coldload16.bin
• Serial flash: coldloadserflash.bin

That cold loader can then receive the Pilot BIOS at 57600bps into RAM starting at 0x6000, and jump into it to receive the regular BIOS and program into RAM or flash.

• Parallel flash with 8-bit RAM: pilot.bin
• Parallel flash with 16-bit RAM: pilot16.bin
• Serial flash: pilotserflash.bin

(The COLDLOAD_serflash_boot.c program is the source of the triplets stored in Lib/Rabbit4000/BIOSLIB/serial_flash_boot_loader.lib and included in Lib/Rabbit4000/BIOSLIB/StdBios.c to bootstrap Rabbit 5000 and 6000 boards from a serial flash.)