Identification register in our older device CY7C1373D is to support the JTAG feature. Please note, we support JTAG feature only in BGA devices and it is not there in TQFP devices. Please refer the pinout diagrams in the datasheet of CY7C1373D, you can see that the JTAG pins (TDO, TDI, TMS, TCK) are not present in TQFP package. So, the identification register is not applicable for TQFP devices and our new devices CY7C1373KV33 are available only in TQFP package.
Both the devices CY7C1373D-100AXC and CY7C1373KV33-100AXC has 100 pin TQFP package, both of them will not support JTAG feature and identification register is not applicable for them. These two devices are pin to pin compatible and there will not be any issues while moving from CY7C1373D-100AXC to CY7C1373KV33-100AXC.