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Architecture
594
SPRUH82C – April 2013 – Revised September 2016
Copyright © 2013–2016, Texas Instruments Incorporated
Enhanced Direct Memory Access (EDMA3) Controller
17.2.3.7.1 Constant Addressing Mode Transfers/Alignment Issues
If either SAM or DAM is set to 1 (constant addressing mode), then the source or destination address must
be aligned to a 256-bit aligned address, respectively, and the corresponding BIDX should be an even
multiple of 32 bytes (256 bit). The EDMA3CC does not recognize errors here but the EDMA3TC asserts
an error, if this is not true. See
NOTE:
The constant addressing (CONST) mode has limited applicability. The EDMA3 should be
configured for the constant addressing mode (SAM/DAM = 1) only if the transfer source or
destination (on-chip memory, off-chip memory controllers, slave peripherals) support the
constant addressing mode. See your device-specific data manual to verify if constant
addressing mode is supported. If the constant addressing mode is not supported, the similar
logical transfer can be achieved using the increment (INCR) mode (SAM/DAM = 0) by
appropriately programming the count and indices values.
17.2.3.7.2 Element Size
The EDMA3 controller does not use the concept of element-size and element-indexing. Instead, all
transfers are defined in terms of all three dimensions: ACNT, BCNT, and CCNT. An element-indexed
transfer is logically achieved by programming ACNT to the size of the element and BCNT to the number of
elements that need to be transferred. For example, if you have 16-bit audio data and 256 audio samples
that needed to be transferred to a serial port, this can be done by programming the ACNT = 2 (2 bytes)
and BCNT = 256.