
DMA CONTROLLER
13-100
13.9 DMA transfer time
7721 Group User’s Manual
(3)
Transfer of array state
In the following cases, the processing in an array state and the first 1-unit transfer are performed
sequentially. (Refer to “Figures 13.8.10 and 13.8.11.”)
Array chain transfer mode: the first transfer of each block
Link array chain transfer mode: the first transfer of each block
Right to use
bus
Array state
CPU
DMAC
CPU
Transfer
Transition
Transition
Fig. 13.9.3 Transfer of array state
Transition of the right to use bus from CPU to DMAC: 1 cycle
Array state:
The number of transfer parameters
× the number of reads of a transfer parameter × the number
of bus cycles for a read + 1 cycle (Refer to “Table 13.9.1.”)
DMA transfer per 1-unit transfer:
In 2-bus cycle transferRead cycle + Write cycle
(Add a value which satisfies the read/write conditions. Refer to “Table 13.4.1.”)
In 1-bus cycle transferRefer to “Table 13.4.5.”
Transition of the right to use bus from DMAC to CPU: 1 cycle
[Example]
Link array chain transfer mode, external data bus width = 16 bits, 2-bus cycle transfer, transfer unit
=16 bits, and under the following conditions:
Transfer source: address direction = forward, start address of data = even, with Wait
Transfer destination: address direction = backward, start address of data =odd, with Wait
+ + + = 1 + 25 + (3 + 4) + 1 = 34 cycles
Table 13.9.1 Time required for processing in array state
External data
bus width
Mode
Transfer method
Array
chain
transfer mode
16 bits
(Including internal bus)
8 bits
16 bits
(Including internal bus)
Link array chain
transfer mode
2-bus cycle transfer
1-bus cycle transfer
2-bus cycle transfer
1-bus cycle transfer
2-bus cycle transfer
1-bus cycle transfer
2-bus cycle transfer
3
2
3
2
4
3
4
3
1-bus cycle transfer
2
4
2
4
3
× 2 × 3 + 1 = 19
2
× 2 × 3 + 1 = 13
3
× 4 × 3 + 1 = 37
2
× 4 × 3 + 1 = 25
4
× 2 × 3 + 1 = 25
3
× 2 × 3 + 1 = 19
4
× 4 × 3 + 1 = 49
3
× 4 × 3 + 1 = 37
Time required for
processing in array state
(Unit:
φ cycle)
Number of reads of
a transfer parameter
Number of transfer
parameters