SH7721 datasheet(1083/1524 Pages) RENESAS

1083 / 1524 page

Section 30

SIM Card Module (SIM)

Rev. 3.00 Jan. 18, 2008 Page 1021 of 1458

REJ09B0033-0300

Hence the receive margin can be expressed as follows.

Formula for receive margin in smart card mode:

M =

( 0.5

−

)

−− D − 0.5

( L

− 0.5 ) F

( L + F )

× 100%

where

M: Receive margin (

N: Ratio of the bit rate to the clock (N = 372)

D: Clock duty (D = 0 to 1.0)

L: Frame length (L = 10)

F: Absolute value of the deviation of the clock frequency

In the above formula, if F = 0 and D = 0.5, then the receive margin is as follows.

When D = 0.5, F = 0, M = (0.5

− 1/2 × 372) × 100%

= 49.866%.

(2)

Retransmit Operation

Retransmit operations when the smart card interface is in receive mode and in transmit mode are

described below.

(a)

Retransmission when the smart card interface is in receive mode (T = 0)

Figure 30.8 shows retransmit operations when the smart card interface is in receive mode. Step (1)

to step (5) of figure 30.8 correspond to the following operation.

1. If an error is detected as a result of checking the received parity bit, the PER bit in SCSSR is

automatically set to 1. At this time, if the RIE bit in SCSCR is set to enable, an ERI request is

issued. The PER bit in SCSSR should be cleared to 0 before the sampling timing for the next

parity bit.

2. The RDRF bit in SCSSR is not set for frames in which a parity error occurs.

3. If no error is detected as a result of checking the received parity bit, the PER bit in SCSSR is

not set.

4. If no error is detected as a result of checking the received parity bit, it is assumed that

reception was completed normally, and the RDRF bit in SCSSR is automatically set to 1. If the

RIE bit in SCSCR is 1 and the EIO bit is 0, an RXI request is generated.

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