AX.25 Modem
CMX7031/CMX7041
7.3
Function Image™ Load and Activation
The Function Image™ (FI) file, which defines the operational capabilities of the device, may be obtained
from the CMLTechnical Portal, following product registration. This is in the form of a ‘C’ header file which
can be included into the host controller software or programmed into an external serial memory. The
maximum possible size of Function Image™ is 46 kbytes, although a typical FI will be less than this. Note
that the BOOTEN pins are only read at power-on or following a C-BUS General Reset and must remain
stable throughout the FI loading process. Once the FI load has completed, the BOOTEN pins are ignored
by the CMX7031/CMX7041 until the next power-up or C-BUS General Reset.
The BOOTEN pins are both fitted with internal low-current pull-down devices.
For C-BUS load operation, both pins should be pulled high by connecting them to VDD either directly or via
a 220kΩ resistor (see Table 2).
For serial memory load, only BOOTEN1 needs to be pulled high in a similar manner, however, if it is
required to program the serial memory in-situ from the host, either a jumper to VDD or a link to a host I/O
pin should be provided to pull BOOTEN2 high when required (see Table 2).
Once the FI has been loaded, the CMX7031/CMX7041 performs these actions:
1. The product identification code $7031 is reported in C-BUS register $C5
2. The FI version code is reported in C-BUS register $C9
3. The two 32-bit FI checksums are reported in C-BUS register pairs $A9, $AA and $B8, $B9
4. The device waits for the host to load the 32-bit Device Activation Code to C-BUS register $C8
5. once activated, the device initialises fully, enters idle mode and becomes ready for use, and the
Programming Flag (bit 0 of the Status register, $C6) will be set.
The checksums should be verified against the published values to ensure that the FI has loaded correctly.
Once the FI has been activated, the checksum, product identification and version code registers are
cleared and these values are no longer available. If an invalid activation code is loaded, the device will
report the value $DEAD in register $A9 and become unresponsive to all further host commands (including
General Reset). A power-on reset is required to recover from this state.
The Device Activation Codes are available from the CML Technical Portal. The checksum values are
shown in the FI header.
Table 2 BOOTEN Pin States
BOOTEN2
BOOTEN1
C-BUS Host load
reserved
Serial Memory load
No FI load
1
1
0
0
1
0
1
0
Note:
In the rare event that a General Reset needs to be issued without the requirement to re-load the
FI, the BOOTEN pins must both be cleared to '0' before issuing the Reset command. The
Checksum values will be reported and the Device Activation code will need to be sent in a
similar manner as that shown in Figure 8. There will not be any FI loading delay. This assumes
that a valid FI has been previously loaded and that VDD has been maintained throughout the
reset to preserve the data.
2013 CML Microsystems Plc
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