EM260-BBRD-128K-USART-R Ember, EM260-BBRD-128K-USART-R Datasheet - Page 25

• Manufacturer Part Number: EM260-BBRD-128K-USART-R
• Description: EM260 BREAKOUT BOARD
• Manufacturer: Ember
• Type: Transceiver, 802.15.4/ZigBeer

Specifications of EM260-BBRD-128K-USART-R

• Frequency: 2.4GHz
• For Use With/related Products: EM260
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: 636-1026

5.3
nHOST_INT
nRESET
nWAKE
nSSEL
SPI Protocol Timing
SCLK
MOSI
MISO
t1
•
•
•
•
•
Figure 7 illustrates all critical timing parameters in the SPI Protocol. These timing parameters are a result of
the EM260’s internal operation and both constrain Host behavior and characterize EM260 operation. The
parameters shown are discussed elsewhere in this document. Note that Figure 7 is not drawn to scale, but is
instead drawn only to illustrate where the parameters are measured.
Wake
Oversized Payload Frame: If the transaction includes a Payload Frame, the Length Byte cannot be a value
greater than 133. If the EM260 detects a length byte greater than 133, it will drop the incoming Command
and abort the entire transaction. The EM260 will then assert nHOST_INT after Slave Select returns to Idle
to inform the Host through an error code in the Response section what has happened. Not only is the
Command in the problematic transaction dropped by the EM260, but the next Command is also dropped,
because it is responded to with the Oversized Payload Frame Error Response.
Aborted Transaction: An aborted transaction is any transaction where Slave Select returns to Idle
prematurely and the SPI Protocol dropped the transaction. The most common reason for Slave Select
returning to Idle prematurely is the Host unexpectedly resetting. If a transaction is aborted, the EM260 will
assert nHOST_INT to inform the Host through an error code in the Response section what has happened.
When a transaction is aborted, not only does the Command in the problematic transaction get dropped by
the EM260, but the next Command also gets dropped since it is responded to with the Aborted Transaction
Error Response.
Missing Frame Terminator: Every Command and Response must be terminated with the Frame Terminator
byte. The EM260 will drop any Command that is missing the Frame Terminator. The EM260 will then
immediately provide the Missing Frame Terminator Error Response.
Long Transaction: A Long Transaction error occurs when the Host clocks too many bytes. As long as the
inter-command spacing requirement is met, this error condition should not cause a problem, since the
EM260 will send only
Command section.
Unresponsive: Unresponsive can mean the EM260 is not powered, not fully booted yet, incorrectly
connected to the Host, or busy performing other tasks. The Host must wait the maximum length of the
Wait section before it can consider the EM260 unresponsive to the Command section. This maximum length
is 200 milliseconds, measured from the end of the last byte sent in the Command Section. If the EM260
ever fails to respond during the Wait section, it is valid for the Host to consider the EM260 unresponsive
and to reset the EM260. Additionally, if nHOST_INT does not assert within 10ms of nWAKE asserting during
the wake handshake, the Host can consider the EM260 unresponsive and reset the EM260.
t2
t3
0xFF
Reset
outside of the Response section as well as ignore incoming bytes outside of the
t4
Figure 7. SPI Protocol Timing Waveform
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t5
Command
<data>
t6
Wait
t7
Response
t8
<data>
t9
t10
EM260
120-0260-000J