CC2510_15 Datasheet, PDF(151/245 Page) Texas Instruments – Low-Power SoC (System-on-Chip) with MCU, Memory,2.4 GHz RF Transceiver, and USB Controller

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CC2510_15 Datasheet, PDF (151/245 Pages) Texas Instruments – Low-Power SoC (System-on-Chip) with MCU, Memory,2.4 GHz RF Transceiver, and USB Controller

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CC2511F8 - Not Recommended for New Designs

12.14.2.3 Slave Select pin (SSN)

When the USART is operating in SPI slave

mode, a 4-wire interface is used with the Slave

Select (SSN) pin as an input to the SPI (edge

controlled). The SPI slave becomes active

after a falling edge on SSN and will receive

data on the MOSI input and send data on the

MISO output. After a rising edge on SSN, the

SPI slave is inactive and will not receive data.

Note that the MISO output is not tri-stated

when the SPI slave is inactive. Also note that

the rising edge on SSN must be aligned to the

CC2510Fx / CC2511Fx

end of the byte sent / received. If this is not the

case, the next received byte will be corrupted.

If there is a rising edge on SSN in the middle

of a byte, this should be followed by a USART

flush to avoid corruption of the following byte.

In SPI master mode, the SSN pin is not used.

When the USART operates as an SPI master

and a slave select signal is needed by an

external SPI slave device, a general purpose

I/O pin should be used to implement the slave

select signal function in software.

Figure 41: SPI Dataflow

12.14.3 Baud Rate Generation

An internal baud rate generator set up the

UART baud rate when operating in UART

mode and the SPI master clock frequency

when operating in SPI mode.

The

UxBAUD.BAUD_M[7:0]

and

UxGCR.BAUD_E[4:0] registers define the

baud rate used for UART transfers and the

rate of the serial clock (SCK) for SPI transfers.

The baud rate is given by the following

equation:

Baudrate

=

(256 +

BAUD _ M ) â 2BAUD _ E

2 28

âF

where F is the system clock frequency set by

the selected system clock source.

The register values required for standard baud

rates are shown in Table 55 (F = 26 MHz) and

Table 56 (24 MHz). The tables also give the

difference in actual baud rate to standard baud

rate value as a percentage error.

The maximum baud rate for UART mode is

F/16 (UxGCR.BAUD_E[4:0]=16 and

UxBAUD.BAUD_M[7:0]=0).

The maximum baud rate for SPI master mode

and thus SCK frequency is F/8

(UxGCR.BAUD_E[4:0]=17

and

UxBAUD.BAUD_M[7:0]=0). If SPI master

mode does not need to receive data, the

SWRS055G

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