Multi-Tech Systems Modem Module MT3334SMI - Manual (Page 69)

Appendixes
MT3334SMI 69
3.3. The packets sent to the modem must be presorted by address and aligned on 128 byte
boundaries (ie. each packet must start on an address that is a multiple of 128).
3.4. The packets should also be a minimum of 128 bytes with the non-programmed bytes set to
the hex value of FF.
3.5. The packets sent to the modem must not span a 4K boundary (ie. start the packet before it
and go over the boundary in the middle of the packet).
3.6. The 10 millisecond delay between M’s at the beginning of the handshake is so that the
modem can sync up to the start bit. If the M’s are sent one right after another, a data bit might
be mistaken as a start bit.
3.7. Multi-Tech firmware files are in Intel Hex Format and must be read in and formatted into 128-
4096 byte blocks before being sent to the modem.
Refer to the Intel Hex Format section below for information about the Intel Hex Format.
Intel Hex Format
An Intel Format Hex File is a text file consisting of “records”, one per line, that start with a “:”
character and include only digits 0-9 and letters A-F. There are three different record types: Extended
Address Records, Data Records and End of File Records.
Data records contain the actual data that is to be programmed into a device. The address contained
in the data record needs to be combined with an extended address (by adding the extended address
shifted four bits left to the data record address) to determine the actual programming address for the
data. If no extended address record is before a given data record in the file, then the extended
address value is assumed to be zero.
The record types are described below:
Data Record
Char Pos Field Type Value Description
1 Record Start “:”
2-3 Data Byte Count “NN” Maximum value is FF (which is 255 data
bytes).
Typical is 20h which causes the hex record
to fit in 80 columns.
4-7 Address “XXXX” Lower 16 bits of 20 bit address, most
significant byte first. This must be added to
Extended Address left shifted four bits.
Char Pos Field Type Value Description
8-9 Record Type “02” Data Record
10+N Data Bytes “YY..YY” The data bytes in hex. Each byte is two
characters.
NN+1,2 Checksum “ZZ” Zero minus the two’s complement addition
of all data hex values.
NN+3,4 End of Line “\r\n” Carriage Return followed by a Line Feed
Example Data Record in Intel Format
:2000A0005BB66DDBB66CD8B060C183060D1B366DDBB66DDBB76FDFBF7EFDFBF6EDDBB66DD4