Using The Slave Interfaces - Altera Cyclone V Device Handbook

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2013.12.30

Using the Slave Interfaces

The slave interfaces connect the DMAC to the level 4 (L4) main bus and enable a microprocessor to access
the registers. Using these registers, a microprocessor can perform the following functions:
• Access the status of the DMA manager thread
• Access the status of the DMA channel threads
• Enable or clear interrupts
• Enable events
• Execute an instruction for the DMAC by programming the following debug registers:
• DBGCMD register
• DBGINST0 register
• DBGINST1 register
Issuing Instructions to the DMAC using a Slave Interface
When the DMAC is operating, you can only issue the following instructions:
• DMAGO Starts a DMA transaction using a DMA channel that you specify
• DMASEV Signals the occurrence of an event, or interrupt, using an event number that you specify
• DMAKILL Terminates a thread
You must ensure that you use the appropriate slave interface, depending on the security state in which the
boot_manager_ns signal initializes the DMAC. For example, if the DMAC is in the Secure state, you
must issue the instruction using the secure slave interface, otherwise the DMAC ignores the instruction.
You can use the secure or non-secure slave interface to start or restart a DMA channel when the DMAC is
in the Non-secure state.
Note: Before you can issue instructions using the debug instruction registers or the DBGCMD register, you
must read the DBGSTATUS register to ensure that debug is idle, otherwise the DMAC ignores the
instructions.
The DMAC immediately processes any instructions received from a slave interface, unless the pipeline is
busy processing another instruction.
Note: Prior to issuing DMAGO, you must ensure that the system memory contains a suitable program for
the DMAC to execute, starting at the address that the DMAGO specifies.
Using DMAGO with the Debug Instruction Registers
The following example shows the necessary steps to start a DMA channel thread using the debug instruction
registers:
1. Create a program for the DMA channel.
2. Store the program in a region of system memory.
3. Program one of the slave interfaces on the DMAC to a DMAGO instruction as follows:
a. Poll the DBGSTATUS register to ensure that debug is idle, and the dbgstatus bit is 0
b. Write to the DBGINST0 register and enter all of the following:
DMA Controller
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Using the Slave Interfaces
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