Table 5-1 Simultaneous Access Behavior; Figure 5-1 Single-Port Ram Dma Interface - ARM ARM966E-S Technical Reference Manual

5.1.2 Dual-port RAM DMA solution
ARM DDI 0186A
CPU RAM access
SP DMA access
CPU read data
CLK
If the data RAM is implemented using dual-port RAM, the second port is used
exclusively for DMA. The CPU and DMA can access the data RAM simultaneously so
the core does not need to be stalled. A dual-port RAM DMA solution provides higher
performance than the single-port solution, but uses a larger die area. The programmer
must ensure that DMA and CPU do not access the same memory locations
simultaneously. The behavior of accessing the same memory locations simultaneously
is either undefined or illegal. Simultaneous access behavior is summarized in Table 5-1.
Copyright © 2000 ARM Limited. All rights reserved.
Addr
WriteEnable
ChipSelect
DataIn
1
ByteWrite
Single Port
RAM
0
Q
RAMRData

Figure 5-1 Single-port RAM DMA interface

Table 5-1 Simultaneous access behavior

Core
access
Read
Direct Memory Access (DMA)
ARM966E-S
DMA Inputs
DMA
Port
DMA Outputs
DMAEnable
DMA
behavior
access
Read Valid
5-3