EM260-RTR datasheet(25/50 Pages) SILICONIMAGE

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EM260

Page 25

120-0260-000M Rev 1.1

unsupported by the current Mode the EM260 is in. Bootloader Frames can only be used with the bootloader

and EZSP Frames can only be used with the EZSP.

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 0xFF outside of the Response section as well as ignore incoming bytes outside of the

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 300

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 300ms of nWAKE asserting during the wake

handshake, the Host can consider the EM260 unresponsive and reset the EM260.

5.3

SPI Protocol Timing

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.

Figure 7. SPI Protocol Timing Waveform

<data>

nSSEL

MISO

MOSI

SCLK

<data>

nHOST_INT

nWAKE

nRESET

t10

Reset

Command

Wait

Response

Wake

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