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CHAPTER 6 DMA FUNCTIONS (DMA CONTROLLER)
146
User’s Manual U14492EJ5V0UD
6.6 Transfer Target
6.6.1 Transfer type and transfer target
Table 6-1 shows the relationship between the transfer type and transfer target (
√
: transfer enabled,
×
: transfer
disabled).
Table 6-1. Relationship Between Transfer Type and Transfer Target
Destination
Internal ROM
On-Chip
Peripheral I/O
Note
Internal RAM
External Memory,
External I/O
On-chip peripheral I/O
Note
×
√
√
√
External I/O
×
√
√
√
Internal RAM
×
√
×
√
External memory
×
√
√
√
S
Internal ROM
×
×
×
×
Note
If the transfer target is the on-chip peripheral I/O, only the single transfer mode can be used.
Cautions 1. The operation is not guaranteed for combinations of transfer destination and source marked
with “
×
” in Table 6-1.
2.
Addresses between 3FFF000H and 3FFFFFFH cannot be specified for the source and
destination address of DMA transfer. Be sure to specify an address between FFFF000H and
FFFFFFFH.
Remark
If the target of the DMA transfer is an on-chip peripheral I/O register (transfer source/transfer
destination), be sure to specify the same transfer size as the register size. For example, in the case of
DMA transfer to an 8-bit register, be sure to specify byte (8-bit) transfer.
<16-bit transfer>
Transfer from a 16-bit bus to an 8-bit bus
A read cycle (16 bits) is generated and then a write cycle (8 bits) is generated twice successively.
Transfer from an 8-bit bus to a 16-bit bus
A read cycle (8 bits) is generated twice successively and then a write cycle (16 bits) is generated.
Data is written to the transfer destination from the lowest byte in little-endian mode, and the highest
byte in big-endian mode.
<8-bit transfer>
Transfer from a 16-bit bus to an 8-bit bus
A read cycle (the higher 8 bits go into a high-impedance state) is generated and then a write cycle (8
bits) is generated.
Transfer from an 8-bit bus to a 16-bit bus
A read cycle (8 bits) is generated and then a write cycle (the higher 8 bits go into a high-impedance
state) is generated. Data is written to the transfer destination from the lowest byte in little-endian
mode, and the highest byte in big-endian mode.