CP2105 Ver la hoja de datos (PDF) - Silicon Laboratories
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CP2105 Datasheet PDF : 24 Pages
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CP2105
6.1. ECI Baud Rate Generation
The baud rate generator for the enhanced interface is very flexible, allowing the user to request any baud rate in
the range from 300 bps to 2.0 Mbps. If the baud rate cannot be directly generated from the 48 MHz oscillator, the
device will choose the closest possible option. The actual baud rate is dictated by Equation 1 and Equation 2.
Clock Divider = -----------------------------------------4---8-----M-----H----z------------------------------------------
2 Prescale Requested Baud Rate
Prescale = 4 if Requested Baud Rate 365 bps
Prescale = 1 if Requested Baud Rate 365 bps
Equation 1. Clock Divider Calculation
Actual Baud Rate = -2---------P----r---e----s---c---a--4--l-8-e----M-----HC----z-l-o---c---k-----D----i--v---i-d---e----r
Prescale = 4 if Requested Baud Rate 365 bps
Prescale = 1 if Requested Baud Rate 365 bps
Equation 2. Baud Rate Calculation
Most baud rates can be generated with an error of less than 1.0%. A general rule of thumb for the majority of UART
applications is to limit the baud rate error on both the transmitter and the receiver to no more than ±2%. The clock
divider value obtained in Equation 1 is rounded to the nearest integer, which may produce an error source. Another
error source will be the 48 MHz oscillator, which is accurate to ±0.25%. Knowing the actual and requested baud
rates, the total baud rate error can be found using Equation 3.
Baud Rate Error (%) = 100 1 – R-----e--A-q---c-u--t-eu---s-a--t-l-e--B-d---a--B-u---a-d---u--R-d---a--R-t--e-a----t-e-- 0.25%
Equation 3. Baud Rate Error Calculation
The UART also supports the transmission of a line break. The length of time for a line break is programmable from
1 to 125 ms, or it can be set to transmit indefinitely until a stop command is sent from the application.
7. GPIO Mode and Modem Mode
Each interface on the CP2105 can be configured in either GPIO Mode or Modem Mode. This allows the SCI and
ECI to have either modem control signals or GPIO signals available at various pins. Table 11 shows the functions
that are available in each mode.By default, both interfaces are configured for GPIO Mode.
Table 11. CP2105 Modem Mode and GPIO Mode
Interface
Standard
Communications
Interface
Enhanced
Communications
Interface
Pin #
24
23
22
1
15
14
17
Modem Mode
DCD_SCI
DTR_SCI
DSR_SCI
RI_SCI
DTR_ECI
DSR_ECI
RI_ECI
GPIO Mode
GPIO_0_SCI
GPIO_1_SCI
GPIO_2_SCI
SUSPEND_SCI
GPIO_0_ECI
GPIO_1_ECI
SUSPEND_ECI
Only one mode can be selected for each interface. Also, the mode of the CP2105 can only be configured once and
cannot be reset to the default configuration after being programmed. Refer to “AN223: Port Configuration and
GPIO for CP210x” for more information on how to configure the port pins of the CP2105.
Rev. 1.0
13
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