CC2500-RTR1 datasheet(24/96 Pages) TI

24 / 96 page

CC2500

SWRS040C

Page 24 of 89

by the radio hardware (e.g. MARCSTATE or

TXBYTES

there

small,

but

finite,

probability that a single read from the register

being

corrupt.

example,

the

probability of any single read from TXBYTES

being corrupt, assuming the maximum data

rate is used, is approximately 80 ppm. Refer to

the

CC2500 Errata Notes [1] for more details.

10.4

Command Strobes

Command strobes may be viewed as single

byte instructions to

CC2500. By addressing a

command strobe register, internal sequences

will be started. These commands are used to

disable the crystal oscillator, enable receive

mode, enable wake-on-radio etc. The 13

command strobes are listed in Table 34 on

page 57.

The command strobe registers are accessed

by transferring a single header byte (no data is

being transferred). That is, only the R/W bit,

the burst access bit (set to 0), and the six

address bits (in the range 0x30 through 0x3D)

are written. The R/W bit can be either one or

zero

and

will

determine

how

the

FIFO_BYTES_AVAILABLE

field in the status

byte should be interpreted.

When writing command strobes, the status

byte is sent on the SO pin.

A command strobe may be followed by any

other SPI access without pulling CSn high.

However, if an SRES strobe is being issued,

one will have to wait for SO to go low again

before the next header byte can be issued as

shown in Figure 8. The command strobes are

executed immediately, with the exception of

the SPWD and the SXOFF strobes that are

executed when CSn goes high.

Figure 8: SRES Command Strobe

10.5

FIFO Access

The 64-byte TX FIFO and the 64-byte RX

FIFO are accessed through the 0x3F address.

When the R/W bit is zero, the TX FIFO is

accessed, and the RX FIFO is accessed when

the R/W bit is one.

The TX FIFO is write-only, while the RX FIFO

is read-only.

The burst bit is used to determine if the FIFO

access is a single byte access or a burst

access.

The

single

byte

access

method

expects a header byte with the burst bit set to

zero and one data byte. After the data byte a

new header byte is expected; hence, CSn can

remain low. The burst access method expects

one header byte and then consecutive data

bytes until terminating the access by setting

CSn

high.

The following header bytes access the FIFOs:



0x3F: Single byte access to TX FIFO



0x7F: Burst access to TX FIFO



0xBF: Single byte access to RX FIFO



0xFF: Burst access to RX FIFO

When writing to the TX FIFO, the status byte

(see Section 10.1) is output for each new data

byte on SO, as shown in Figure 7. This status

byte can be used to detect TX FIFO underflow

while writing data to the TX FIFO. Note that

the status byte contains the number of bytes

free before writing the byte in progress to the

TX FIFO. When the last byte that fits in the TX

FIFO is transmitted on SI, the status byte

received concurrently on SO will indicate that

one byte is free in the TX FIFO.

The TX FIFO may be flushed by issuing a

SFTX

command strobe. Similarly, a SFRX

command strobe will flush the RX FIFO. A

SFTX

or SFRX command strobe can only be

issued in the IDLE, TXFIFO_UNDERLOW or

RXFIFO_OVERFLOW states. Both FIFOs are

flushed when going to the SLEEP state.

Figure 9 gives a brief overview of different

10.6

PATABLE

Access

The 0x3E address is used to access the

PATABLE

, which is used for selecting PA

power control settings. The PATABLE is an 8-

byte table, but not all entries into this table are

used. The entries to use are selected by the 3-

bit value FREND0.PA_POWER.



When

using

2-FSK,

GFSK,

MSK

modulation only the first entry into this

table is used (index 0).

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