A N 9 3
134
Rev. 1.4
A CRC can be run on the upgrade file loaded into on-chip Program RAM with the AT&T6 command to verify that
the upgrade was correctly written to the on-chip memory. The CRC value obtained from executing the AT&T6
command should match the CRC value provided with the upgrade code.
5.9. Escape Methods
There are four ways to escape from data mode and return to command mode once a connection is established.
Three of these, +++, “9th Bit”, and the “Escape Pin”, allow the connection to be maintained while one or both
modems are in the command mode. The fourth method is to terminate the connection. The three escape methods
that maintain the connection are combined by a logical OR. For example, if +++ and the “Escape Pin” are both
enabled, either returns the modem to the command mode from the data mode. In parallel or SPI mode, the escape
pin is not available. Instead the system can set the ESC flag in Hardware Interface Register 1 (HIR1).
While in data mode, an escape to command mode occurs if an escape command is sampled as negated for at
least 60 ms, then sampled asserted for at least 60 ms. The modem is then prepared to accept AT commands,
regardless of whether OK has been sent to the host. If the modem is already in command mode, the modem does
not send OK. The host should always wait for OK before entering the next command after an escape.
When making a new connection, the host must not try to escape between the connect message and the protocol
message. An escape attempt in this interval may fail because the modem is not in data mode until after the
protocol message. In practice, it is difficult to determine the exact boundary between command mode and data
mode. The recommendation is to time the escape command 100 ms low and 100 ms high, and expect that the
modem has transitioned to command mode.
The system should then flush the receive buffer 100 ms after the escape command has been removed, send AT,
and wait for OK. This ensures that the modem is in command mode because OK is caused by the AT command
and not by the escape command.
5.9.1. +++ Escape
The +++ escape is enabled by default and is controlled by U70 [13] (TES). There are equal guard time periods
before (leading) and after (trailing) the +++ set by the register S12, during which there must be no interface (UART,
SPI or parallel) activity. If this inactivity criterion is met, the ISOmodem escapes to the command mode at the end
of the S12 time period following the +++. Any activity in the host interface during either the leading or trailing time
period causes the ISOmodem to ignore the escape request and remain in data mode. Timing for this escape
sequence is illustrated in Figure 29.
Table 96. Load Technique and Speed Table*
Start Condition
Delay
Between
Lines
Load time, 6235-Byte
Patch, 115 kbaud UART
Approach Used With
Reset, then
ATE0 and ATQ1
0.5 ms
0.694
Embedded systems
1 ms
0.771
Embedded systems
2 ms
0.925
Embedded systems
5 ms
1.385
Embedded systems
10 ms
2.152
Embedded systems
Reset
Wait for OK
3.998
Windows or embedded system where
time precision is worse than 10 ms
Reset
100 ms
15.962
Windows without writing a patch loader
*Note:
The delay times do not include the time to empty the UART's possibly long TX buffer. The time quoted is between the
end of transmission of the last character of a line and the start of transmission of the first character of the next line.
Summary of Contents for Si2404
Page 2: ...AN93 2 Rev 1 4 ...
Page 200: ...AN93 200 Rev 1 4 Figure 31 TAM Handset and Speakerphone Voice Paths ...
Page 201: ...AN93 Rev 1 4 201 Figure 32 Si3000 Codec Gain and Signal Selection Options ...
Page 290: ...AN93 290 Rev 1 4 Figure 57 256 Band Spectral Display Figure 58 2048 Band Spectral Display ...
Page 305: ...AN93 Rev 1 4 305 Figure 76 Parallel or SPI Port Interrupt Service Flowchart ...