Microchip Technology megaAVR 0 Series Manual page 291

Table 22-4. Formula Nomenclature
Symbol
D
R
slow
R
fast
The following tables list the maximum receiver baud rate error that can be tolerated. Normal Speed mode
has higher toleration of baud rate variations.
Table 22-5. Recommended Maximum Receiver Baud Rate Error for Normal Speed Mode (CLK2X =
0)
D #(Data + Parity Bit) R
5
6
7
8
9
10
Table 22-6. Recommended Maximum Receiver Baud Rate Error for Double Speed Mode (CLK2X =
1)
D #(Data + Parity Bit) R
5
6
7
8
9
10
The recommendations of the maximum receiver baud rate error were made under the assumption that
the receiver and transmitter equally divide the maximum total error.
22.3.2.5 USART in Master SPI mode
Using the USART in Master SPI mode requires the transmitter to be enabled. The receiver can optionally
be enabled to serve as the serial input. The XCK pin will be used as the transfer clock.
As for the USART, a data transfer is initiated by writing to the USARTn.DATA register. This is the case for
both sending and receiving data since the transmitter controls the transfer clock. The data written to
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2018 Microchip Technology Inc.
Universal Synchronous and Asynchronous Recei...
Meaning
Sum of character size and parity size (D = 5 to 10 bit)
The ratio of the slowest incoming data rate that can be accepted in relation to the
receiver baud rate
The ratio of the fastest incoming data rate that can be accepted in relation to the
receiver baud rate
[%] R [%] Maximum Total Error [%] Receiver Max. Receiver
slow fast
93.20 106.67
94.12 105.79
94.81 105.11
95.36 104.58
95.81 104.14
96.17 103.78
[%] R [%] Maximum Total Error [%] Receiver Max. Receiver
slow fast
94.12 105.66
94.92 104.92
95.52 104.35
96.00 103.90
96.39 103.53
96.70 103.23
+6.67/-6.80
+5.79/-5.88
+5.11/-5.19
+4.58/-4.54
+4.14/-4.19
+3.78/-3.83
+5.66/-5.88
+4.92/-5.08
+4.35/-4.48
+3.90/-4.00
+3.53/-3.61
+3.23/-3.30
Datasheet Preliminary
®
megaAVR 0-Series
Error [%]
±3.0
±2.5
±2.0
±2.0
±1.5
±1.5
Error [%]
±2.5
±2.0
±1.5
±1.5
±1.5
±1.0
DS40002015A-page 291