CHAPTER 6 DMA FUNCTIONS (DMA CONTROLLER)
User’s Manual U12688EJ4V0UM00
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6.13 Boundary of Memory Area
The transfer operation is not guaranteed if the source or the destination address is over the area of DMA objects
(external memory, internal RAM, external I/O, or internal peripheral I/O) during DMA transfer.
6.14 Transfer of Misalign Data
16-bit DMA transfer of misalign data is not supported. If the source or the destination address is set to an odd
address, the LSB bit of the address is forcibly accepted as “0”.
6.15 Clocks of DMA Transfer
Table 6-3 lists the overhead before and after DMA transfer and minimum execution clock for DMA transfer.
Table 6-3. Minimum Execution Clock in DMA Cycle
From accepting DMARQn to falling edge of DMAAKn
4 clocks
External memory access
Refer to miscellaneous memory and I/O cycle
Internal RAM access
2 clocks
Internal peripheral I/O access
3 clocks
From rising edge of DMAAKn to falling edge of TCn
1 clock
Remark
n = 0 to 3
6.16 Maximum Response Time to DMA Request
Under the conditions shown below, the response time to a DMA request becomes the maximum time (this is the
state permitted by the DRAM refresh cycle).
(1) Condition 1
Condition
Instruction fetch from external memory at the 8-bit data bus width
Response time
Tinst
×
4 + Tref
Fetch (1/4) Fetch (2/4) Fetch (3/4) Fetch (4/4)
Refresh
DMA cycle
DMARQn (input)
DMAAKn (output)
D0 to D15 (input/output)
Содержание V850E/MS1 UPD703100
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