Contents
How to calculate the clock mismatch for UART?
(16 internal clock cycles per bit) × (1 start bit + 8 data bits + ½ a stop bit) = (16) × (9.5) = 152 UART receive clocks after the original falling edge of the START bit. Now we can calculate our allowable error as a percentage. For the normal scenario, the clock mismatch error can be ±5/152 = ±3.3%.
What is the error budget for UART normal link?
UART “normal link” is sampled reliably within 75% of bit time. For Figures 4 and 5, we can determine that the error budget is ±25% and ±37.5% from the optimal bit-center sampling point for the nasty and normal scenarios, respectively. This error is equivalent to ±4 or ±6 periods of the 16x UART receive clock.
Can a baud be shared between two UARTs?
So presuming that both UARTs are attempting to communicate at exactly the same bit rate (baud), the allowable error can be shared, in any proportion, between the two UARTs. Making use of the allowable error budget is helpful in systems where both ends of the link are being designed at the same time.
What causes a UART to make a timing error?
These errors point to a mismatch in the transmit UART and receive UART timing that is consistent during a frame. Since the timing is synchronized at the falling edge of the START bit, the worst-case timing error will be at the last data sampling point, which is the STOP bit1.
How to troubleshoot a serial connection in Cisco?
This chapter presents general troubleshooting information and a discussion of tools and techniques for troubleshooting serial connections. The chapter consists of the following sections: The output of the show interfaces serial exec command displays information specific to serial interfaces.
When do two UARTs communicate, is there no clock?
When two UARTs communicate, it is a given that both transmitter and receiver know the signaling speed. The receiver does not know when a packet will be sent (no receiver clock); hence, the protocol is termed “asynchronous.” The receiver circuitry is correspondingly more complex than that of the transmitter.
What is the proper status of a serial line?
Table 15-1 Serial Lines: show interfaces serial Status Line Conditions This is the proper status line condition. No action is required. The router is not sensing a CD 2 signal (that is, the CD is not active). A telephone company problem has occurred—line is down or is not connected to CSU 3 /DSU 4 .