
Autoinitialization
11-34
11.9 Autoinitialization
Autoinitialization is a method for reloading a DMA channel register file when
the transfer counter goes to zero. When the DMA channel is operating in
autoinitialization mode, the link pointer register and auxiliary link pointer regis-
ter are used to initialize the registers that control the operation of the DMA
channel. These pointers are memory address locations for blocks of data that
are to be loaded into the DMA register file, shown in Figure 11–1. Link pointers
are covered in subsection 11.3.4, Link Pointer and Auxiliary Link–Pointer Reg-
isters
Autoinitialization is a regular DMA block transfer operation in which the des-
tination is the DMA coprocessor’s register file. The DMA reads the value
pointed to by the link pointer and writes it to the DMA register over the periph-
eral bus on the next available cycle. Consequently, autoinitialization read/write
accesses are also subject to any normal CPU/DMA access conflict.
Autoinitialization can happen:
Without CPU intervention when the TRANSFER MODE bits = 10
2
 (autoin-
itialization 1). Refer to subsection 11.8.3, Running in TRANSFER MODE
= 10
2
 (Autoinitialization 1)
With CPU intervention when the TRANSFER MODE bits = 11
2
 (autoinitial-
ization 2). In this case, the CPU should restart the DMA channel before the
autoinitialization proceeds. Refer to subsection 11.8.4, Running in
TRANSFER MODE = 11
2
 (Autoinitialization 2)
Before any block transfer (autoinitialization method a). The DMA starts
with the transfer counter at zero, then autoinitializes and performs a block
transfer.
After a block transfer (autoinitialization method b). The DMA starts with a
regular block transfer, and, when the transfer counter register goes to
zero, it autoinitializes.
Autoinitialization 1 or 2 can use methods a or b.
Autoinitialization depends on the DMA channel’s current mode: split or unified
mode. The mode of operation is controlled by the SPLIT MODE bit (bit 14 in
Figure 11–2). When autoinitializing the DMA coprocessor, do not changethe
SPLIT MODE bit. This bit should be changed onlywhen the DMA coprocessor
has been reset and halted (see DMA START bit description in Table 11–5 for
more information).