H8S2245 datasheet(538/818 Pages) RENESAS

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Section 13 Smart Card Interface

Rev.3.00 Mar. 26, 2007 Page 496 of 772

REJ09B0355-0300

Interrupt Operation

There are three interrupt sources in smart card interface mode: transmit data empty interrupt (TXI)

requests, transfer error interrupt (ERI) requests, and receive data full interrupt (RXI) requests. The

transmit end interrupt (TEI) request is not used in this mode.

When the TEND flag in SSR is set to 1, a TXI interrupt request is generated.

When the RDRF flag in SSR is set to 1, an RXI interrupt request is generated.

When any of flags ORER, PER, and ERS in SSR is set to 1, an ERI interrupt request is generated.

The relationship between the operating states and interrupt sources is shown in table 13.8.

Table 13.8

Smart Card Mode Operating States and Interrupt Sources

Operating State

Flag

Enable Bit

Interrupt

Source

DTC

Activation

Transmit Mode

Normal

operation

TEND

TIE

TXI

Possible

Error

ERS

RIE

ERI

Not possible

Receive Mode

Normal

operation

RDRF

RIE

RXI

Possible

Error

PER, ORER

RIE

ERI

Not possible

Data Transfer Operation by DTC

In smart card mode, as with the normal SCI, transfer can be carried out using the DTC. In a

transmit operation, the TDRE flag is also set to 1 at the same time as the TEND flag in SSR, and a

TXI interrupt is generated. If the TXI request is designated beforehand as a DTC activation

source, the DTC will be activated by the TXI request, and transfer of the transmit data will be

carried out. When DISEL in DTC is 0 and the transfer counter value is not 0, the TDRE and

TEND flags are automatically cleared to 0 when data transfer is performed. If DISEL is 1, or if

DISEL is 0 and the transfer counter value is 0, the DTC writes the transfer data to TDR but does

not clear the flags. Therefore, the flags should be cleared by the CPU. In the event of an error, the

SCI retransmits the same data automatically. The TEND flag remains cleared to 0 during this time,

and the DTC is not activated. Thus, the number of bytes specified by the SCI and DTC are

transmitted automatically even in retransmission following an error. However, the ERS flag is not

cleared automatically when an error occurs, and so the RIE bit should be set to 1 beforehand so

that an ERI request will be generated in the event of an error, and the ERS flag will be cleared.

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