NXP Semiconductors MPC5644A, Reference Manual, Page: 1362 / 1735

Enhanced Serial Communication Interface (ESCI)
MPC5644A Microcontroller Reference Manual, Rev. 6
1362 Freescale Semiconductor
The maximum percent difference between the receiver baud rate and the transmitter baud rate is:
Eqn. 31-6
The maximum percent differences for the supported frames is given in Table 31-23
31.4.4.2 Slower receiver tolerance
In this case the receiver has a slower baud rate than the transmitter, thus the stop bit sampling is still
running while the next start bit is already transmitted. To ensure the correct, noise and framing error free
reception of the stop bit, the samples RS8, RS9, and RS10 must be located in the transmitted stop bit as
shown in
Figure 31-24 .
Figure 31-24. Slower Receiver
The maximum tolerance that ensures error free reception can be calculated with the assumption, that RS11
is sampled in the transmitted start bit and RS10 is sampled in the last stop bit.
For an frame with n payload bits and s stop bits, the transmitter starts the transmission of the next start bit
Eqn. 31-7
after the start of the transmission of the previous start bit.
For an frame with n payload bits and s stop bits, the receiver samples the RS10 sample of the last stop bit
Eqn. 31-8
after the successful qualification of the start bit.
To ensure error free reception of the last stop bit, the transmitter must start the transmission of the start bit
after the receiver samples RS10.
Eqn. 31-9
Table 31-23. Faster Receiver Maximum Tolerance
payload bits max baudrate difference tx
STOP
rx
STOP
8 4.63% 144 151
9 4.19% 160 167
13 3.03% 224 231
baudrate

rx
STOP
tx
STOP
–
rx
STOP
---------------------------------------
 
 
100
 
RCLK
START BIT
RXD
START BIT
QUALIFICATION
6 7 8 2 1 3
RSC
8 9 10
DATA
VOTING
LAST STOP BIT
11
tx
START
n s 1 + +
 
= 16 RT
TR
 
rx
STOP
n s +
 
= 16 RT
RE
9 RT
RE

+
 
rx
STOP
tx
START
