NVM_SUM
if (checksum != NVM_SUM && !(*data))
if (checksum != NVM_SUM) {
checksum = NVM_SUM - checksum;
if (checksum != NVM_SUM) {
checksum = NVM_SUM - checksum;
checksum = NVM_SUM - checksum;
if (checksum != NVM_SUM) {
checksum = NVM_SUM - checksum;
checksum = NVM_SUM - checksum;
if (checksum != NVM_SUM) {
checksum = NVM_SUM - checksum;