Hitachi SH7750 Hardware Manual page 776

From the above equation, if F = 0 and D = 0.5, the receive margin is 49.866%, as given by the
following equation.
When D = 0.5 and F = 0:
M = (0.5 – 1/2 × 372) × 100% = 49.866%
(2) Retransfer Operations
Retransfer operations are performed by the SCI in receive mode and transmit mode as described
below.
Retransfer Operation when SCI is in Receive Mode: Figure 17.11 illustrates the retransfer
operation when the SCI is in receive mode.
1. If an error is found when the received parity bit is checked, the PER bit in SCSSR1 is
automatically set to 1. If the RIE bit in SCSCR1 is enabled at this time, an ERI interrupt
request is generated. The PER bit in SCSSR1 should be cleared to 0 before the next parity bit
is sampled.
2. The RDRF bit in SCSSR1 is not set for a frame in which an error has occurred.
3. If an error is found when the received parity bit is checked, the PER bit in SCSSR1 is not set to
1.
4. If no error is found when the received parity bit is checked, the receive operation is judged to
have been completed normally, and the RDRF bit in SCSSR1 is automatically set to 1. If the
RIE bit in SCSCR1 is enabled at this time, an RXI interrupt request is generated.
5. When a normal frame is received, the pin retains the high-impedance state at the timing for
error signal transmission.
nth transfer frame
Ds D0 D1 D2 D3 D4 D5 D6 D7 Dp
RDRF
PER
Figure 17.11 Retransfer Operation in SCI Receive Mode
Rev. 6.0, 07/02, page 726 of 986
Retransferred frame
DE Ds D0 D1 D2 D3
2
1
(DE)
D4 D5 D6 D7 Dp
5
4
3
Transfer frame n+1
Ds D0 D1 D2 D3 D4