28 USB FUNCTION CONTROLLER (USB)
S1C33L26 TECHNICAL MANUAL
Seiko Epson Corporation
28-61
When the DMA is set to be in the free run mode by the setting of the CountMode bit of the DMA_
Config_1 register (CountMode = 0), values transmitted by the DMA can be referred at any time. In
this mode, when the DMA Transfer Byte Counter exceeds 0xffffffff, it returns to 0x00000000 and the
DMA_CountUp bit of the DMA_IntStat register is set to 1.
When the DMA is set to be in the countdown mode by the setting of the CountMode bit of the DMA_
Config_1 register (CountMode = 1), specify the total number of transmissions in the DMA Transfer
Byte Counter, set the DMA_Go bit of the DMA_Control register to 1, and then start the DMA transfer.
In this mode, the DMA Transfer Byte Counter is decreased as much as the data quantity transferred by
the DMA. When it reaches 0x00000000, the DMA ends. In this mode, the remained quantity of the data
to transfer can be referred. Writing into these registers during the DMA transfer is neglected.
For reading these registers, access the DMA_Count_HH, HL, LH and LL registers in this order.