CHAPTER 7 DMAC
Preliminary User’s Manual A14874EJ3V0UM
151
7.3 Transfer Objects
(1) Transfer types
Table 7-1 shows the relationships between transfer types and transfer objects.
Caution Operation is not guaranteed when a transfer is performed using a combination of transfer
source and transfer destination marked by an “No” in Table 7-1.
Table 7-1. Relationships Between Transfer Type and Transfer Object
Transfer Destination
Two-Cycle Transfer
Flyby Transfer
VSB
NPB
RAM
VSB
NPB
RAM
VSB
Yes
Yes
Yes
Yes
Note
No
No
NPB
Yes
Yes
Yes
No
No
No
Transfer
Source
RAM
Yes
Yes
Yes
No
No
No
Note
The transfer can be performed only when using the MEMC (NT85E500) associated with the flyby transfer.
Remark
Yes: Transfer enabled
No: Transfer disabled
VSB: External memory or peripheral macro on the VSB
NPB: Peripheral macro on the NPB
RAM: RAM directly connected to the VDB
(2) Wait function
Table 7-2 shows the relationships between the wait function and transfer objects.
Table 7-2. Relationships Between Wait Function and Transfer Object
Transfer Object
Wait Function
VSB
Set by MEMC (NT85E500, NT85E502)
NPB
Set by VSWC register
RAM
No wait
7.4 DMA Channel Priorities
DMA channel prioritization is fixed as follows.
DMA channel 0 > DMA channel 1 > DMA channel 2 > DMA channel 3
This prioritization is only valid in the TI state. During a block transfer, the channel used for transfer is never
switched.
During a single-step transfer, if a higher priority DMA transfer request is generated during the period when the bus
is released (TI), the higher priority DMA transfer is performed.