SH7721 datasheet(1081/1524 Pages) RENESAS

1081 / 1524 page

Section 30

SIM Card Module (SIM)

Rev. 3.00 Jan. 18, 2008 Page 1019 of 1458

REJ09B0033-0300

(6)

Data Transfer Using DMAC

The smart card interface enables reception and transmission using the DMAC.

In transmission, when the TDRE flag in SCSSR is set to 1, a DMA transfer request for transmit

data empty is issued. If a DMA transfer request for transmit data empty is set in advance as a

DMAC activation source, the DMAC can be activated and made to transfer data when a DMA

transfer request for transmit data empty occurs.

When in T = 0 mode and if an error signal is received during transmission, the same data is

automatically retransmitted. At the time of this retransmission, no DMA transfer request is issued,

and so the number of bytes specified to the DMAC can be transmitted.

When using the DMAC for transmit data processing and performing error processing as a result of

an interrupt request sent to the CPU, the TIE bit should be cleared to 0 so that no TXI requests are

generated, and the RIE bit should be set to 1 so that an ERI request is issued. The ERS flag set

when an error signal is received is not cleared automatically, and so should be cleared by sending

an interrupt request to the CPU.

In receive operation, when the RDRF flag in SCSSR is set to 1, a DMA transfer request for

receive data full is issued. By setting a DMA transfer request for receive data full in advance as a

DMAC activation source, the DMAC can be activated and made to transfer data when a DMA

transfer request for receive data full occurs.

When in T = 0 mode and if a parity error occurs during reception, a data retransmit request is

issued. At this time the RDRF flag is not set, and a DMA transfer request is not issued, so the

number of bytes specified to the DMAC can be received.

When using the DMAC for receive data processing and performing error processing as a result of

an interrupt request sent to the CPU, the RIE bit should be set to 1 and the EIO bit to 1, so that no

RXI requests are generated and only ERI requests are generated.

The PER, ORER, and WAIT_ER flags that are set by a receive error are not automatically cleared,

and so should be cleared by sending an interrupt request to the CPU.

When using the DMAC for transmission and reception, the DMAC should always be set first and

put into the enabled state, before setting the smart card interface.

SH7721 Datasheet(PDF) 1081 Page - Renesas Technology Corp