ST7260E1 STMicroelectronics, ST7260E1 Datasheet - Page 80

• Manufacturer Part Number: ST7260E1
• Description: LOW SPEED USB 8-BIT MCU FAMILY WITH UP TO 8K FLASH/ROM AND SERIAL COMMUNICATION INTERFACE (SCI)
• Manufacturer: STMicroelectronics

Specifications of ST7260E1

• 4 Or 8 Kbytes Program Memory: high density Flash (HDFlash), or FastROM with readout and write protection

Serial communications interface (SCI)
Note:
80/139
1
2
clock occurs just before the pin value changes, the samples would then be out of sync by
~4 µs. This means the entire bit length must be at least 40 µs (36µs for the 10th sample +
4 µs for synchronization with the internal sampling clock).
Clock deviation causes
The causes which contribute to the total deviation are:
●
●
●
●
All the deviations of the system should be added and compared to the SCI clock tolerance:
Noise error causes
See also description of Noise error in
Start bit
The noise flag (NF) is set during start bit reception if one of the following conditions occurs:
A valid falling edge is not detected. A falling edge is considered to be valid if the 3
consecutive samples before the falling edge occurs are detected as '1' and, after the falling
edge occurs, during the sampling of the 16 samples, if one of the samples numbered 3, 5 or
7 is detected as a “1”.
During sampling of the 16 samples, if one of the samples numbered 8, 9 or 10 is detected as
a “1”.
Therefore, a valid Start Bit must satisfy both the above conditions to prevent the Noise Flag
getting set.
Data bits
The noise flag (NF) is set during normal data bit reception if the following condition occurs:
●
Therefore, a valid Data Bit must have samples 8, 9 and 10 at the same value to prevent the
Noise Flag getting set.
D
transmitter is transmitting at a different baud rate).
D
D
the reception of one complete SCI message assuming that the deviation has been
compensated at the beginning of the message.
D
During the sampling of 16 samples, if all three samples numbered 8, 9 and10 are not
the same. The majority of the 8th, 9th and 10th samples is considered as the bit value.
TRA
QUANT
REC
TCL
: Deviation due to the transmission line (generally due to the transceivers)
: Deviation due to transmitter error (Local oscillator error of the transmitter or the
: Deviation of the local oscillator of the receiver: This deviation can occur during
: Error due to the baud rate quantisation of the receiver.
D
TRA
+ D
QUANT
Receiver on page
+ D
REC
+ D
TCL
76.
< 3.75%
ST7260xx