Block Transfer Mode; Receive Data Sampling Timing And Reception Margin - Renesas RZ/A Series User Manual

RZ/A1L Group, RZ/A1LU Group, RZ/A1LC Group
15.6.3

Block Transfer Mode

Block transfer mode is different from normal smart card interface mode in the following respects.
• Even if a parity error is detected during reception, no error signal is output. Since the PER bit in SSR is set by error
detection, clear the PER bit before receiving the parity bit of the next frame.
• During transmission, at least 1 etu is secured as a guard time from the end of the parity bit until the start of the next
frame.
• Since the same data is not re-transmitted during transmission, the TEND flag in SSR is set 11.5 etu after
transmission start.
• In block transfer mode, the ERS flag in SSR indicates the error signal status as in normal smart card interface mode,
but the flag is always read as 0 because no error signal is transferred.
15.6.4

Receive Data Sampling Timing and Reception Margin

Only the internal clock generated by the on-chip baud rate generator can be used as a transfer clock in smart card
interface mode.
In this mode, the SCI can operate on a base clock with a frequency of 32, 64, 372, 256, 93, 128, 186, or 512 times the bit
rate according to the settings of the BCP2 bit in SCMR and the BCP[1:0] bits in SMR (the frequency is always 16 times
the bit rate in normal asynchronous mode).
For data reception, the falling edge of the start bit is sampled with the base clock to perform internal synchronization.
Receive data is sampled on the 16th, 32nd, 186th, 128th, 46th, 64th, 93rd, and 256th rising edges of the base clock so that
it can be latched at the middle of each bit as shown in Figure 15.29. The reception margin here is determined by the
following formula.
1
M = (0.5 - ) - (L - 0.5) F -
2N
M: Reception margin (%)
N: Ratio of bit rate to clock (N = 32, 64, 372, 256)
D: Duty cycle of clock (D = 0 to 1.0)
L: Frame length (L = 10)
F: Absolute value of clock frequency deviation
Assuming values of F = 0, D = 0.5, and N = 372 in the above formula, the reception margin is determined by the formula
below.
M = {0.5 - 1/(2 × 372)} × 100 [%] = 49.866%
R01UH0437EJ0600 Rev.6.00
Jan 29, 2021
D - 0.5
(1+F)
×100 [%]
N
15. Serial Communications Interface
15-50