Does KDS requires additional tools to generate srec s3 format of output file ?
'only S3' S19 files is probably not what you want and need. You can generate different formats of files (intel hex, binary, srec/S-Record/S19 files).
See section "Creating Binary Files with GNU ARM Eclipse Plugins" in http://mcuoneclipse.com/2014/04/20/binary-files-for-the-mbed-bootloader-with-eclipse-and-gnu-arm-eclipse-plugins/.
Additinally, there is the
option in the GNU objcopy tool which can be used to specify the srecord length, and there is
to force S3 records, see https://mcuoneclipse.com/2013/10/29/s-record-manipulation-with-gnu-objcopy-and-burner-utility/
I hope this helps,
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