DMC-1000
Chapter 4 Communication
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Chapter 4 Communication
Introduction
The DMC-1000 receives commands from a PC/XT/AT or compatible computer. The controller is
configured as a standard AT style card that is mapped into the I/O space. Communication between the
DMC-1000 and the computer is in the form of ASCII characters where data is sent and received via
READ and WRITE registers on the DMC-1000. A handshake is required for sending and receiving
data.
The DMC-1000 contains a 512 character write FIFO buffer. This permits sending commands at high
speeds ahead of their actual processing by the DMC-1000. The DMC-1000 also contains a 512
character read buffer.
This chapter discusses Address Selection, Communication Register Description, A Simplified Method
of Communication, Advanced Communication Techniques, and Bus Interrupts.
Address Selection
The DMC-1000 address, N, is selectable by setting the Address Dip Switches A2, A3, A4, A5, A6, A7
and A8, where A2 represents 2
2
, A3 represents 2
3
bit and so on. Setting a switch to the ON position
sets that bit to zero and setting a switch to the OFF position sets that bit to 1. Please note that this
discussion refers only to the computer address of the controller and is not related to specifying axes for
instructions.
The default address of the DMC-1000 is 1000 (A4 and A2 switches ON).
The DMC-1000 can be configured for any 4th address between 512 and 1024. It is the responsibility
of the user to assure there are no address conflicts between the DMC-1000 and the computer. The
DMC-1000 must not conflict with an address used by the PC or another I/O card.
WARNING: The DMC-1000 address setting must not conflict with an address used by the PC or
another I/O card. An address conflict will prevent communication or cause data conflicts resulting
in lost characters.
To select an address (N), first make sure it is a number between 512 and 1024 that is divisible by four.
Then subtract 512 from N and use the switches A2 through A8 to represent the binary result. A switch
in the ON position represents a binary 0 and the OFF position represents binary 1.
Example - Address Selection
1. Select address, N, as 996.
2. Check to see if N is divisible by 4.
3. Subtract 512 from N.
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