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USER MANUAL Chapter 4 Communication • 45
Chapter 4 Communication
Introduction
The DMC-13X8 receives commands from the VME host. The controller is configured as a standard
6U VME style card that resides in the 16 bit short I/O space. Communication between the DMC-13X8
and the computer is in the form of ASCII or binary characters where data is sent and received via
READ and WRITE registers on the DMC-13X8. A handshake is required for sending and receiving
data.
For communication, the DMC-13X8 contains a 512 character write FIFO buffer. This permits sending
commands at high speeds ahead of their actual processing by the DMC-13X8. The DMC-13X8
contains a 512 character read buffer. The DMC-13X8 also provides a secondary, read-only
communication channel for fast access to data. The second communication channel is used as a
Polling FIFO for high speed access to parameters or system information.
The DMC-13X8 may be addressed in either the supervisory or user modes. To address this space, the
address modifier lines of the VME Bus must be set to the following.
AM5 AM4 AM3 AM2 AM1 AM0
1 0 1 X 0 1
Every VME CPU can do this but it is necessary to consult your specific CPU board’s manual for
proper configuration of address modifiers.
This chapter discusses Address Selection, Communication Register Description, A Simplified Method
of Communication, Advanced Communication Techniques, and Bus Interrupts.
Communication with Controller
Communication Registers
Register Description Address Read/Write
READ for receiving data N+1 Read only
WRITE for transmitting data N+1 Write only
CONTROL for status control N+3 Read and Write
The DMC-13X8 provides three registers used for communication. The READ register and WRITE
register occupy address N+1 and the CONTROL register occupies address N+3 in the I/O space. The
READ register is used for receiving data from the DMC-13X8. The WRITE register is used to send