H83069RF datasheet(239/1003 Pages) RENESAS

239 / 1003 page

Rev. 5.0, 09/04, page 217 of 978

7.4.2

I/O Mode

I/O mode can be selected independently for each channel.

One byte or word is transferred at each transfer request in I/O mode. A designated number of

these transfers are executed. One address is specified in the memory address register (MAR), the

other in the I/O address register (IOAR). The direction of transfer is determined automatically

from the activation source. The transfer is from the address specified in IOAR to the address

specified in MAR if activated by an SCI channel 0 receive-data-full interrupt, and from the

address specified in MAR to the address specified in IOAR otherwise.

Table 7.6 indicates the register functions in I/O mode.

Table 7.6

Function

Activated by

SCI 0 Receive-

Data-Full

Interrupt

Other

Activation

Initial Setting

Operation

MAR

Destination

address

Source

address

Destination or

source start

address

Incremented or

decremented

once per

transfer

All 1s

IOAR

Source

address

Destination

address

Source or

destination

address

Held fixed

ETCR

Transfer counter

Number of

transfers

Decremented

once per

transfer until

H'0000 is

reached and

transfer ends

[Legend]

MAR:

Memory address register

IOAR: I/O address register

ETCR: Execute transfer count register

MAR and IOAR specify the source and destination addresses. MAR specifies a 24-bit source or

destination address, which is incremented or decremented as each byte or word is transferred.

IOAR specifies the lower 8 bits of a fixed address. The upper 16 bits are all 1s. IOAR is not

incremented or decremented.

Figure 7.2 illustrates how I/O mode operates.

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