38K2 datasheet(74/151 Pages) RENESAS

74 / 151 page

38K2 Group

Rev.3.00

Oct 15, 2006

page 74 of 147

REJ03B0193-0300

qP33/ExINT pin

Any one of the following signals for this pin can be selected:

•TxB_RDY (transmit buffer ready) output

•RxB_RDY (receive buffer ready) output

•Mch_req (memory channel request) output

Either TxB_RDY or RxB_RDY is normally selected. The memory

channel request is for an access request signal to the memory

channel.

In a small system, a data transfer processing to the internal

memory is performed in the interrupt routine. According to that

situation, the 38K2 group has the function automatically to switch

an interrupt factor attached on the interrupt pin by program.

qP40/ExDREQ/RxD pin

This pin is a port at the initial state. Which signal can be set by

program.

•RxB_RDY (receive buffer ready) output

•Mch_req (memory channel request) output

Mch_req of DMAC is normally selected. The output method of the

memory channel request signal depends on the burst bit (BURST)

of memory channel operation mode register. When the burst bit is

“0”, this signal is periodically output at each 1-byte transfer. (See

Figures 124 and 127.)

When the burst bit is “1”, this signal is continuously output while

the memory address counter is counting from the beginning ad-

dress to the end address (See Figures 125 and 128.)

qP41/ExDACK/TxD pin

This pin is a port at the initial state. The DMA acknowledge signal

can be set by program.

The DMA acknowledge signal DACK = “L” is the same state as

that of CS = “L” and A0 = “L”. Access to multichannel RAM is

started by a rise of read signal or write signal which is set during

this term.

Note: If the DMA acknowledge signal and the chip select signal

are simultaneously active (DACK = “L” and CS = “L”), also

set the address signal A0 to “L”. If A0 is “H”, the memory

channel and the CPU channel are activated simultaneously

and it might cause some error.

qP42/ExTC/SCLK pin

This pin is a port at the initial state. The terminal count signal can

be set by program.

If the terminal count signal is set at one bus cycle while a memory

channel operation write is being performed, the 38K2 group con-

firms that its bus cycle is the write cycle of the last data and sets

the memory channel status bits to “112”, and the interrupt is gener-

ated and the memory channel operation ends even if the memory

address counter has not reached the end address.

The CPU can obtain the last address where the data is written by

reading out the value of memory address counter. (See Figure

126.)

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