MARION SYSTEMS MS68K (01) PDF Document

The MARION SYSTEMS MS68K requires only +5 volts DC at 1.5 amps to operate. It uses a connector identical to those used on most 5 1/4″ floppy and hard disks.

TABLE 1. Power Connector (J5)

Port A of the DUART on the MARION SYSTEMS MS68K is initialized as follows:

• 9600 Baud
• 8 Bits per Character
• 1 Stop Bit
• No Parity

TABLE 2. Terminal Connector (J3)

Port B of the DUART on the MARION SYSTEMS MS68K is initialized as follows:

• 1200 Baud
• 8 Bits per Character
• 1 Stop Bit
• No Parity

TABLE 3. Modem Connector (J2)

The MARION SYSTEMS MS68K utilizes a 1772-type floppy controller to interface up to two 5 1/4″ or 3 1/2″ floppy drives. The interface requires a power cable and a signal cable.

For most 5 1/4″ floppy drives, the mating connectors for the signal cable are:

• MOLEX 15-29-0341
• 3M 3463-0001

For most 3 1/2″ floppy drives, typical mating connectors for the signal cable are:

• AMP 499496-9
• MOLEX 15-29-8342

NOTE: On certain 3 1/2″ drives, the mechanical keying on the drive itself is such that the “V-mark”, which normally designates Pin 1, will instead be designating Pin 34.

For single floppy drive connections, ensure only the “Drive Select 0” jumper is installed, and terminating resistors are installed. For two drives, one should only have its “Drive Select 0” jumper installed and the second drive should only have its “Drive Select 1” jumper installed. Only the drive at the end of the signal cable, furthest from the MARION SYSTEMS MS68K, should have its terminating resistors installed.

TABLE 4. Floppy Connector (J4)

The SCSI interface on the MARION SYSTEMS MS68K uses a 50-pin connector with the following signal definitions:

TABLE 5. SCSI Connector (J1)

TABLE 6. Parallel Printer (J6)

The signals controlling density, side select, and drive select originate from the 68681 DUART output port, requiring specific 68000 instructions to set or reset the corresponding output bits (OP3, OP4, OP5, OP6):

To select Side 0 or Side 1 (OP3):

• Select Side 0: move.b #$08,$E8001D
• Select Side 1: move.b %$08,$E8001F

To select/deselect Drive 0 (OP4):

• Select Drive 0: move.b #$10,$E8001F
• Deselect Drive 0: move.b #$10,$E8001D

To select/deselect Drive 1 (OP5):

• Select Drive 1: move.b %$20,$E8001F
• Deselect Drive 1: move.b #$20,$E8001D

To select Single/Double Density (OP6):

• Select Single Density: move.b %$40,$E8001F
• Select Double Density: move.b %$40,$E8001D

Prior to performing the above set and reset commands, the output port configuration register must be cleared to all zeroes with the following instruction:

move.b %$00,E8001B

Example to Configure the 1772 for Side 0, Drive 0 and Double Density:

• Set bits OP3, OP5 and OP6: move.b #$68,$E8001D
• Reset bit OP4: move.b #$10,$E8001F

The states of the four status signals from the printer are input to the microprocessor through the 68681 DUART input port, located at $E8001B in the microprocessor read memory space. The bits assigned to these signals are:

Input Bit | Function | 68000 Test Instruction

To generate the appropriate pulse to strobe the data to the printer (STROBE- signal, Active LOW):

1. Test if printer not busy: btst.b %2,$E8001B
2. Set STROBE low: move.b #$80,$E8001D
3. Set STROBE high: move.b #$80,$E8001F

To control INIT- (Initialize, Active LOW):

• Initialize (to LOW state): move.b #$04,$E8001D
• Initialize (to HIGH state): move.b %$04,$E8001F

To control STROBE- (Strobe, Active LOW):

• Strobe (to LOW state): move.b #$80,$E8001D
• Strobe (to HIGH state): move.b #$80,$E8001F

Prior to performing the above set and reset commands for output functions, the output port configuration register must be cleared to all zeroes with the following instruction:

move.b #$00,E8001B ; clear OPCR

The MARION SYSTEMS MS68K system has two memory maps, one for Initial Operation (just following reset) and one for Normal Operation.

Initial Operation Memory Map:

Normal Operation Memory Map:

The decoded addresses for memory and peripheral devices are:

There are five sources of interrupts to the 68000 microprocessor on the MARION SYSTEMS MS68K, listed in order of highest priority to lowest priority:

Entry into the ROM monitor on the MARION SYSTEMS MS68K will occur due to the following conditions:

1. System reset (power-up or auxiliary)
2. Microprocessor Exception error that is not handled by a user program
3. Via a breakpoint (Trap #15)
4. Via a jump from another program (DOS, etc.)

The ROM Monitor commands available on the MARION SYSTEMS MS68K are:

The Assemble (A) command assembles instruction by instruction. Following initial command execution, the present hex code at the given address is shown, followed by a disassembly of that code. A new instruction may then be entered or a will skip to the next instruction. When entering new code, a leading space must be entered unless a label is specifically intended. All data and addresses may be in decimal (default) or hex ($). The DC.W directive is recognized for setting data words (i.e. DC.W $2EFF). The period (.) exits the assembler.

The Breakpoint Display or Change (B) command allows you to set a breakpoint at address [addr]. The instruction will be allowed to execute count times, and will cause a break in execution if it is encountered again. The default count is 0, always causing a break when encountered. If no arguments are given, all active breakpoints are displayed as “address count” in hex. The breakpoints are stored in a special area and are inserted at the specified address(es) when a program is executed with the “G” command. If the program is not exited in a standard way such as applying a direct reset the breakpoints will remain where they have been placed by the “G” command, and the original code will be lost. Up to eight breakpoints may be active at one time.

The Breakpoint Clear (BC) command clears the breakpoint at addr. If no argument is given, all active breakpoints will be cleared.

To use the Change Memory Word (C) command, enter memory word change mode. The given address is shown, followed by the existing word data. One may then enter new data, which replaces the old data (last four digits only, leading zeroes added), a to go to the next word, a < to back one word, or a period (.) to terminate.

The Dump Memory in Hex and ASCII (D) command dumps memory in hex dump and ASCII dump format, 16 bytes to a line. Following command execution in which only the first argument is specified, one line of 16 bytes is displayed in hex byte format, followed on the same line with the ASCII equivalents of those 16 bytes. If a is then given, 16 additional lines are displayed. If both arguments are specified, output is continuous, but can be temporarily halted by depressing ‘S and then continued by pressing any other key. A continuous display can be aborted by depressing ^C. Use period (.) is exit this mode.

To use the Execute Program – No Breakpoints (E) command, execute program at addr. Any existing breakpoints are ignored.

The Fill Memory (F) command fills a memory block between addr1 and addr2 with data. The default size is byte if no size is specified, or “.B” for byte, “.W” for word and “.L” for long.

To use the Go to Program with Breakpoints (G) command, insert active breakpoint(s) and begin program execution at addr. After a breakpoint has occurred, execution may be continued by typing “G” without an argument.

The List Memory Disassembled (L) command lists memory in disassembled format. Upon initial command execution, 16 instructions are shown disassembled. causes 16 additional instructions to be shown. If both arguments are specified, output is continuous, but can be halted by depressing ^S and continued by pressing any other key. A continuous display can be aborted by depressing ^C. Use period (.) is exit.

The Move Memory (M) command moves a memory block between addr1 and addr2 to addr3. Addresses may overlap (i.e. M 100 200 120).

The Memory Set (N) command sets memory starting at addr with data value(s). The default size is byte if no size is specified, or use “.B” for byte, “.W” for word and “.L” for long.

The Register Display (R) command on the MARION SYSTEMS MS68K displays the registers of the microprocessor, including the eight data registers, the eight address registers, the program counter, the status register, the system and user stack pointers.

The Search Memory (S) command searches memory from addr1 to addr2 for a match with data, masked by mask. Execution terminates with the first match. The default size is byte if no size is specified, or use “.B” for byte, “.W” for word and “.L” for long.

The Trace (T) command traces instruction execution an instruction at a time if no count is specified, or the number of instructions specified by count (in hex). As each instruction is traced, execution halts, registers are displayed, along with the next instruction. Additional steps can be performed by typing a for each step.

The Verify Memory (V) command compares the memory block between addr1 and addr2 with the block starting at addr3.

The Memory Test (Y) command executes a memory test. The test program prompts for test parameters.

The Register Change command modifies a single microprocessor register by supplying [regname] and value. Valid names are D0-D7, A0-A7, USP, SSP (or SP), CCR and SR. For example, to modify register D4 to 4FF8: .D4 4FF8.

The Set Port B Baud Rate (Q) command sets the baud rate of port B by executing the “Q” command with a desired baud rate of data from the following set:

• 110
• 300
• 600
• 1200
• 2400
• 4800
• 9600

The DUART may be programmed directly for additional rates.