For more details about features and
additional description information on the device Universal Asynchronous Receiver
Transmitter, see the corresponding subsections within Signal Descriptions and
Detailed Description sections.
Table 6-128 UART Timing Conditions
PARAMETER |
MIN |
MAX |
UNIT |
INPUT CONDITIONS |
SRI |
Input slew
rate |
0.5 |
5 |
V/ns |
OUTPUT CONDITIONS |
CL |
Output load
capacitance |
1 |
30(1) |
pF |
(1) This value represents an absolute
maximum load capacitance. As the UART baud rate increases, it may be necessary
to reduce the load capacitance to a value less than this maximum limit to
provide enough timing margin for the attached device. The output rise/fall times
increase as capacitive load increases, which decreases the time data is valid
for the receiver of the attached devices. Therefore, it is important to
understand the minimum data valid time required by the attached device at the
operating baud rate. Then use the device IBIS models to verify the actual load
capacitance on the UART signals does not increase the rise/fall times beyond the
point where the minimum data valid time of the attached device is violated.
Table 6-129 UART Timing Requirements see Figure 6-109
NO. |
PARAMETER |
DESCRIPTION |
MIN |
MAX |
UNIT |
1 |
tw(RXD) |
Pulse width,
receive data bit high or low |
0.95U(1)(2) |
1.05U(1)(2) |
ns |
2 |
tw(RXDS) |
Pulse width,
receive start bit low |
0.95U(1)(2) |
|
ns |
(1) U = UART baud time in ns =
1/programmed baud rate.
(2) This value defines the data valid time, where the input voltage is required to
be above VIH or below VIL.
Table 6-130 UART Switching
Characteristics see Figure 6-109
NO. |
PARAMETER |
DESCRIPTION |
MIN |
MAX |
UNIT |
|
f(baud) |
Programmable
baud rate for Main Domain UARTs |
|
12 |
Mbps |
Programmable
baud rate for MCU and WKUP Domain UARTs |
|
3.7 |
Mbps |
3 |
tw(TXD) |
Pulse width, transmit data bit high or low |
U(1) - 2 |
U(1) + 2 |
ns |
4 |
tw(TXDS) |
Pulse width, transmit start bit low |
U(1) - 2 |
|
ns |
(1) U = UART baud time in ns = 1/actual baud rate, where the actual baud rate is
defined in the UART Baud Rate Settings table of the device TRM.
For more information, see Universal
Asynchronous Receiver/Transmitter (UART) section in Peripherals
chapter in the device TRM.