Sorry,
My fault
because:
ID CODE is in table 12-4 and the IR length is 6 bits according to the ug332.pdf
so
jtag_device 4 0x1 0x3 0x1c1a093
should be
jtag_device 6 0x1 0x3 0x1c1a093
Also you may still need to work on (I think you need to make sure the ARM is 1st on your physical chain):
#target <type> <startup mode>
#target arm7tdmi <reset mode> <chainpos> <endianness> <variant>
target arm7tdmi little reset_run 0 arm7tdmi-s_r4
working_area 0 0x40000000 0x40000 nobackup
#flash configuration
#flash bank lpc2000 0x0 0x40000 0 0 0 lpc2000_v2 4000 calc_checksum
flash bank lpc2000 0x0 0x40000 0 0 0 lpc2000_v2 12000 calc_checksum