I took a capture of the a SWD transaction, I don't know the protocol but it looks like the ACK works and it responds.
If I try it from the command line this is the output
Type "connect" to establish a target connection, '?' for help
J-Link>connect LPC5502
Please specify device / core. <Default>: LPC5502
Type '?' for selection dialog
Device>
Please specify target interface:
J) JTAG (Default)
S) SWD
T) cJTAG
TIF>s
Specify target interface speed [kHz]. <Default>: 4000 kHz
Speed>
Device "LPC5502" selected.
Connecting to target via SWD
ConfigTargetSettings() start
Disabling flash programming optimizations: Compare, SkipBlankDataOnProg
ConfigTargetSettings() end
InitTarget() start
ERROR: Wrong DM-AP IDCODE detected: 0x00000000
InitTarget() end
ConfigTargetSettings() start
Disabling flash programming optimizations: Compare, SkipBlankDataOnProg
ConfigTargetSettings() end
InitTarget() start
ERROR: Wrong DM-AP IDCODE detected: 0x00000000
InitTarget() end
ConfigTargetSettings() start
Disabling flash programming optimizations: Compare, SkipBlankDataOnProg
ConfigTargetSettings() end
InitTarget() start
ERROR: Wrong DM-AP IDCODE detected: 0x00000000
InitTarget() end
ConfigTargetSettings() start
Disabling flash programming optimizations: Compare, SkipBlankDataOnProg
ConfigTargetSettings() end
InitTarget() start
ERROR: Wrong DM-AP IDCODE detected: 0x00000000
InitTarget() end
Cannot connect to target.
J-Link>