EM260-RCM-USART-R Ember, EM260-RCM-USART-R Datasheet - Page 22

• Manufacturer Part Number: EM260-RCM-USART-R
• Description: EM260 RCM BOARD
• Manufacturer: Ember
• Type: Transceiver, 802.15.4/ZigBeer

Specifications of EM260-RCM-USART-R

• Frequency: 2.4GHz
• For Use With/related Products: EM260
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: 636-1025

5 SPI Protocol
5.1
5.2
120-0260-000J
Physical Interface Configuration
SPI Transaction
The EM260 Low Level Protocol centers on the SPI interface for communication with a pair of GPIO for
handshake signaling.
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The EM260 supports both SPI Slave Mode 0 (clock is idle low, sample on rising edge) and SPI Slave Mode 3
(clock is idle high, sample on rising edge) at a maximum SPI clock rate of 5MHz, as illustrated in Figure 4. The
convention for the waveforms in this document is to show Mode 0.
The nHOST_INT signal and the nWAKE signal are both active low. The Host must supply a pull-up resistor on
the nHOST_INT signal to prevent errant interruptions during undefined events such as the EM260 resetting.
The EM260 supplies an internal pull-up on the nWAKE signal to prevent errant interruptions during undefined
events such as the Host resetting.
The basic EM260 SPI transaction is half-duplex to ensure proper framing and to give the EM260 adequate
response time. The basic transaction, as shown in Figure 5, is composed of three sections: Command, Wait,
and Response. The transaction can be considered analogous to a function call. The Command section is the
function call, and the Response section is the return value.
EM260 – Slave (MISO)
nHOST_INT
Clock, Mode 0 (SCLK)
Clock, Mode 3 (SCLK)
Host – Master (MOSI)
The EM260 looks like a hardware peripheral.
The EM260 is the slave device and all transactions are initiated by the Host (the master).
The EM260 supports a reasonably high data rate.
nSSEL
SCLK
MOSI
MISO
Figure 5. General Timing Diagram for a SPI Transaction
Figure 4. SPI Transfer Format, Mode 0 and Mode 3
Command
MSB
MSB
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Wait
Response
LSB
LSB
EM260