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CYRF6936

Document #: 38-16015 Rev. *F Page 4 of 39

Figure 6-2. Example ACK Packet Format

Packet Buffers

All data transmission and reception utilizes the 16-byte packet

buffers—one for transmission and one for reception.

The transmit buffer allows a complete packet of up to 16-bytes

of payload data to be loaded in one burst SPI transaction, and

then transmitted with no further MCU intervention. Similarly,

the receive buffer allows an entire packet of payload data up

to 16 bytes to be received with no firmware intervention

required until packet reception is complete.

The CYRF6936 IC supports packets up to 255 bytes, however,

actual maximum packet length will depend on accuracy of the

clock on each end of the link and the data mode; interrupts are

provided to allow an MCU to use the transmit and receive

buffers as FIFOs. When transmitting a packet longer than 16

bytes, the MCU can load 16-bytes initially, and add further

bytes to the transmit buffer as transmission of data creates

space in the buffer. Similarly, when receiving packets longer

than 16 bytes, the MCU must fetch received data from the

FIFO periodically during packet reception to prevent it from

overflowing.

Auto Transaction Sequencer (ATS)

The CYRF6936 IC provides automated support for trans-

mission and reception of acknowledged data packets.

When transmitting in transaction mode, the device automati-

cally:

• starts the crystal and synthesizer

• enters transmit mode

• transmits the packet in the transmit buffer

• transitions to receive mode and waits for an ACK packet

• transitions to the transaction end state when either an ACK

packet is received, or a timeout period expires

Similarly, when receiving in transaction mode, the device

automatically:

• waits in receive mode for a valid packet to be received

• transitions to transmit mode, transmits an ACK packet

• transitions to the transaction end state (receive mode to

await the next packet, etc.)

The contents of the packet buffers are not affected by the

transmission or reception of ACK packets.

In each case, the entire packet transaction takes place without

any need for MCU firmware action (providing packets of 16

bytes or less are used); to transmit data the MCU simply needs

to load the data packet to be transmitted, set the length, and

set the TX GO bit. Similarly, when receiving packets in trans-

action mode, firmware simply needs to retrieve the fully

received packet in response to an interrupt request indicating

reception of a packet.

Backward Compatibility

The CYRF6936 IC is fully interoperable with the main modes

of the first generation devices. The 62.5-kbps mode is

supported by selecting 32-chip DDR mode. Similarly, the

15.675-kbps mode is supported by selecting 64-chip SDR

mode.

In this way, a suitably configured CYRF6936 IC device may

transmit data to and/or receive data from a first generation

device. Disabling the SOP, length, and CRC16 fields is

required for backwards compatibility.

Data Rates

By combining the PN code lengths and data transmission

modes described above, the CYRF6936 IC supports the

following data rates:

• 1000-kbps (GFSK)

• 250-kbps (32-chip 8DR)

• 125-kbps (64-chip 8DR)

• 62.5-kbps (32-chip DDR)

• 31.25-kbps (64-chip DDR)

• 15.625-kbps (64-chip SDR)

7.0 Functional Block Overview

2.4-GHz Radio

The radio transceiver is a dual conversion low IF architecture

optimized for power and range/robustness. The radio employs

channel-matched filters to achieve high performance in the

presence of interference. An integrated Power Amplifier (PA)

provides up to +4 dBm transmit power, with an output power

control range of 34 dB in 7 steps. The supply current of the

device is reduced as the RF output power is reduced.

P SOP 1 SOP 2 CRC 16

Pream ble

n x 16us

1st Fram ing

Sym bol*

2nd Fram ing

Sym bol*

CRC field from

received packet.

2 Byte periods

*Note:32 or 64us

Table 7-1. Internal PA Output Power Step Table

PA Setting Typical Output Power (dBm)

7+4

5–5

4 –13

3 –18

2 –24

1 –30

0 –35

1 2 3 4 5 6 7 8 9 ... 38 39

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