m30262f8gp Renesas Electronics Corporation., m30262f8gp Datasheet - Page 72

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

DMAC
66
DMAC
Figure 1.11.1. Block diagram of DMAC
This microcomputer has two DMAC (direct memory access controller) channels that allow data to be sent
to memory without using the CPU. DMAC shares the same data bus with the CPU. The DMAC is given a
higher right of using the bus than the CPU, which leads to working the cycle stealing method. On this
account, the operation from the occurrence of DMA transfer request signal to the completion of 1-word (16-
bit) or 1-byte (8-bit) data transfer can be performed at high speed. Figure 1.11.1 shows the block diagram
of the DMAC. Table 1.11.1 shows the DMAC specifications. Figures 1.11.2 to 1.11.4 show the registers
used by the DMAC.
Either a write to the software DMA request bit or an interrupt request factor are used as a DMA transfer
request signal. The DMA transfer is not affected by the interrupt enable flag (I flag) nor by the interrupt
priority level. The DMA transfer does not affect interrupts.
If the DMAC is active (the DMA enable bit is set to 1), data transfer starts every time a DMA transfer request
signal occurs. If the cycle of the occurrences of DMA transfer request signals is higher than the DMA
transfer cycle, there can be instances in which the number of transfer requests do not agree with the
number of transfers. For details, see the description of the DMA request bit.
DMA0 transfer counter TCR0 (16)
DMA0 transfer counter reload register TCR0 (16)
DMA1 transfer counter reload register TCR1 (16)
DMA1 transfer counter TCR1 (16)
Preliminary Specifications Rev. 0.9
Specifications in this manual are tentative and subject to change.
(addresses 0029
(addresses 0039
Data bus high-order bits
Data bus low-order bits
Renesas Technology Corp.
16
16
, 0028 )
, 0038
16
)
DMA0 forward address pointer (20) (Note)
DMA0 source pointer SAR0(20)
DMA0 destination pointer DAR0 (20)
DMA1 source pointer SAR1 (20)
DMA1 forward address pointer (20) (Note)
DMA latch high-order bits
Note: Pointer is incremented by a DMA request.
SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER
(addresses 0022
(addresses 0032
DMA latch low-order bits
(addresses 0026
(addresses 0036
16
16
to 0020
to 0030
M16C/26 Group
16
16
16
16
to 0024 )
to 0034
)
)
16
)