m30262f8gp Renesas Electronics Corporation., m30262f8gp Datasheet - Page 77

• Manufacturer Part Number: m30262f8gp
• Description: Renesas 16-bit Cmos Single-chip Microcomputer M16c Family / M16c/20 Series
• Manufacturer: Renesas Electronics Corporation.

DMAC
(1) Transfer cycle
(2) DMAC transfer cycles
The transfer cycle consists of the bus cycle in which data is read from memory or from the SFR area
(source read) and the bus cycle in which the data is written to memory or to the SFR area (destination
write). The number of read and write bus cycles depends on the source and destination addresses. Also,
the bus cycle itself is longer when software waits are inserted.
Figure 1.11.5 shows the example of the transfer cycles for a source read. For convenience, the destina-
tion write cycle is shown as one cycle and the source read cycles for the different conditions are shown.
In reality, the destination write cycle is subject to the same conditions as the source read cycle, with the
transfer cycle changing accordingly. When calculating the transfer cycle, remember to apply the respec-
tive conditions to both the destination write cycle and the source read cycle. For example (2) in Figure
1.11.5, if 16-bit data is being transferred from an odd source address to an odd destination address, two
bus cycles are required for both the source read cycle and the destination write cycle.
Any combination of even or odd transfer read and write addresses is possible. Table 1.11.2 shows the
number of DMAC transfer cycles.
The number of DMAC transfer cycles can be calculated as follows:
(a) Effect of source and destination addresses
(b) Effect of software wait
No. of transfer cycles per transfer unit = No. of read cycles x j + No. of write cycles x k
When 16-bit data is transferred on a 16-bit data bus, and the source and destination both start at odd
addresses, there are one more source read cycle and destination write cycle than when the source
and destination both start at even addresses.
When the SFR area or a memory area with a software wait is accessed, the number of cycles is
increased for the wait by 1 bus cycle. The length of the cycle is determined by BCLK.
Preliminary Specifications Rev. 0.9
Specifications in this manual are tentative and subject to change.
Renesas Technology Corp.
SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER
M16C/26 Group
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