Hardware Guide

SD Card Socket

The SD card socket is a Push-Push type. When removing the card, always push in to release the latching mechanism before sliding the card out. Never use force to pull the card out of the socket. The card must be inserted into the socket upside-down (label facing down, contacts facing up). Use only SD or SDHC cards with the CoCo SDC.

Insert the card into the socket before applying power to the CoCo or Mult-Pak Interface. When power is applied, the LED on the CoCo SDC board should light up momentarily. If the LED does not turn off after a few seconds then this is an indication that the card was not recognized by the hardware. This can happen if the card has not been formatted with a FAT16 or FAT32 file system. It could also indicate that the card was not inserted properly or that there is a problem with the CoCo SDC itself.

Although SD cards are hot-swappable, the CoCo SDC firmware does not handle that situation very well. It's recommended that you completely shutdown the CoCo and MPI before swapping cards.

Jumper Settings

The three-pin jumper strip provides two mutually exclusive options for board configuration; Cartridge Auto-Start and Dragon DRQ Mode.  The default setting has neither option enabled (no jumper installed).

Installing a jumper between the center pin and the AUTO pin connects the Q clock to the CART interrupt pin. This causes the computer to automatically start executing the program in the selected Flash bank at power-up. Do NOT use this option to auto-start SDC-DOS or other Disk Basic ROMs.

Installing a jumper between the center pin and the DRQ pin is required for emulation of a Dragon DOS floppy controller (requires firmware version 115 or later). Do NOT install a jumper in this position when using the board with a CoCo.

DIP Switch Settings

The board includes a 4-position DIP switch that is used to configure which bank of Flash is active at power-up or reset and which addressing scheme is used to communicate with the controller.

Make sure the computer's power is off before making any changes to the DIP switch settings!

Three of the switches specify the Flash bank to activate upon power-up or system reset. The switches are labeled on the board as 4, 2 and 1. The eight Flash banks are numbered 0 to 7. Place only those switches whose sum equals the desired bank number into the ON position. For example, to select bank 5, place the switches labeled 4 and 1 into the ON position and leave the switch labeled 2 in the OFF position. The board is provided with SDC-DOS in bank 0 of the Flash and all three switches in the OFF position.

The DRGN switch selects the address scheme for the controller. In the OFF position the controller will use the CoCo address scheme. In the ON position, the controller will use the Dragon DOS address scheme. The different schemes are summarized in the table below.

UsageCoCo AddressDragon Address
Drive Control Latch  FF40  FF48
Flash Data Register  FF42  FF4A
Flash Control Register  FF43  FF4B
Command  /  Status  FF48  FF40
FDC Track Register  /  IO Reg 1  FF49  FF41
FDC Sector Register  /  IO Reg 2  FF4A  FF42
FDC Data Register  /  IO Reg 3  FF4B  FF43