Cypress FM4 Series - Settings of des; Specifying Transfer Data Size

CHAPTER 11: DSTC
FM4 Peripheral Manual, Doc. No. 002-04856 Rev. *E 511
3.1 Settings of DES
This section explains setting details of the DES and operations of the DSTC.
3.1.1 Specifying Transfer Data Size
TW, IRM, IIN, ORM
The DSTC transfers data of the data width specified in TW in DES0 in a single transfer. There is a transfer
number counter in the DSTC. The counter has a dual loop configuration consisting of an outer loop
counter and an inner loop counter. ORM (outer loop remain) in DES1 indicates the remaining number of
transfers of the outer loop counter, and IRM (inner loop remain) in the DES1 Register the remaining
number of transfers of the inner loop counter. IIN (inner loop initial) in DES1 specifies the initial value of
the inner loop counter.
At the start of a transfer, specify the transfer data width and different numbers of transfers in TW, IRM, IIN
and ORM. For one DES, the DSTC transfers data of the total of TW×IIN×ORM.
Table 3-1 shows the method of specifying the transfer data width, the number of transfers and the transfer
mode.
Table 3-1 Specifying Transfer Mode, Transfer Size and Number of Transfers
Area Name
Name
Details
DES0
MODE
MODE selects a transfer mode.
0: Selects mode 0.
1: Selects mode 1.
TW[1:0]
TW specifies the data width in a single transfer.
00: 8 bits (byte)
01: 16 bits (halfword)
10: 32 bits (word)
DES1
IIN
Specifies the initial value of the inner loop counter in the transfer number counter.
IRM
Specifies the remain value of the inner loop counter in the transfer number counter.
ORM
Specifies the remain value of the outer loop counter in the transfer number counter.
MODE
If 0 is written to MODE, the DSTC executes a transfer in mode 0. In this mode, one Start Trigger makes
the DSTC transfer data of the bit width specified in TW for IIN times. After having executed transfers for
the number specified in IIN, the DSTC executes the Chain Start or waits for the next Start Trigger. If Start
Triggers of the amount specified in ORM are sent to the DSTC, the DSTC ends the transfer of the number
(IIN×ORM) specified in the DES.
If 1 is written to MODE, the DSTC executes a transfer in mode 1. In this mode, one Start Trigger makes
the DSTC transfer data of the bit width specified in TW once. After having executed one transfer, the
DSTC executes the Chain Start or waits for the next Start Trigger. If Start Triggers of the amount
equivalent to the result of IIN×ORM are sent to the DSTC, the DSTC ends IIN×ORM times of transfer
specified in the DES.
In the SW transfer, both mode 0 and mode 1 can be used. In the HW transfer, select either mode 0 or
mode 1 depending on the type of peripherals that generates a Start Trigger. To make the DSTC execute a
transfer at a Start Trigger from a peripheral that has to have to a handshake with the DSTC at every data
transfer, use mode 1. In the case of data transfer with the MFS, ADC and USB, since the DSTC transfers
data to the FIFO in a peripheral, use mode 1. In the case of a Start Trigger from a peripheral that notifies
the DSTC of the transfer start timing, such as the timer, the external interrupt block, etc., both mode 0 and
mode 1 can be used.
In mode 0, specifies the settings of ORM and IIN. A value of 1 to 65536 inclusive can be specified in both
ORM and IIN. The setting of IRM does not need to be specified. In the DSTC, the setting of IIN is copied
to IRM.
In mode 1, specifies the settings of ORM, IIN and IRM. A value of 1 to 65536 inclusive can be specified in
ORM. A value of 1 to 256 inclusive can be specified in IIN. Specify the same value in IRM and IIN.