CHAPTER 11: DSTC
FM4 Peripheral Manual, Doc. No. 002-04856 Rev. *E 505
2. DSTC Operations Overview and DSTC System Configuration
This section provides an overview of operations of the DSTC and explains the DSTC system
configuration.
2.1 Operations Overview of DSTC
DES System
The DSTC executes a transfer operation according to the content specified in a DES built on the memory
by the CPU. As shown in Table 2-1, a DES consists of seven settings, DES0 to DES6. The settings
specify transfer basic settings, the number of transfers, the transfer source address and the transfer
destination address in their respective areas. (For details of the bit assignment of each DES, see "5
Registers and Descriptors of DSTC".) These settings are stored in the memory area as a single group.
DES0 to DES6 are all 32 bits (1 word) in size. DES4 to DES6 are optional DES. Their settings may not
need to be specified depending on the content of a transfer.
Table 2-1 Types of DES and Settings
Figure 2-1 illustrates the configuration of the DES System Method of the DSTC. When using the DSTC,
reserve adequate free memory area for storing the DES. Select a memory area that is readable and
writable because the DSTC has to refer to and update the DES. Set (1. in Figure 2-1) the start address of
the memory area using the DESTP (DES-Top-address) register of the DSTC. Multiple DES can be
allocated to a 4096-word (16 Kbyte) area starting from the DESTP. Up to 1024 DES can be allocated in
the area. The DSTC identifies a DES according to its address value (DESP: DES-pointer) relative to the
DES0 area starting from the DESTP.
Start of the Transfer
After transfer information has been stored in a DES (2.in Figure 2-1), the DSTC transfer can be started by
one of the following three start trigger methods.
− Software-Start (SW Start)
The Software-Start is a start trigger method to start the DSTC transfer directly from the CPU. The
transfer is started by writing the DESP of the DES to be used to the SWTR (Software Trigger)
Register (3 in Figure 2-1).Software-Start is called SW Start, and the transfer of the DSTC by SW
Start is called SW Transfer later in this document.
− Hardware-Start (HW Start)
The Hardware-Start is a start trigger method to start the DSTC transfer with the interrupt signal
from a peripheral as a transfer request signal. When an interrupt signal from a peripheral has
been asserted (4 in Figure 2-1), the transfer of the DSTC starts bypassing the CPU. In advance,
write the DESP of the DES of this transfer to the HWDESP register (Hardware DESP)
corresponding to an HW channel in the DSTC (1 in Figure 2-1). Hardware-Start is called HW Start,
and the transfer of the DSTC by HW Start is called HW Transfer later in this document.
− Chain Start
Chain start is a start trigger method that is described in the DES. After the transfer in the DES
ended, If the DES have Chain start trigger, the DSTC starts a new transfer according to the
succeeding DES ( or the same DES ). The new DESP of DES for chain transfer is calculated from
current DESP automatically.
To Next Page
Loading...
