A telemetry protocol for an implantable medical device is disclosed. The sending device forms a block of information to be telemetered to the receiving device, including a header, a message, and an error detection data (CRC1). The entirety of the block is divided into smaller packets of a predetermined size. Each packet has a CRC computed for it (CRC2), and is sent to the receiving device, which deduces a CRC2 and compares it with the appended CRC2. If not valid, that packet is again requested to be resent. If valid, the next packet is requested to be sent, its CRC2 checked, etc., until all packets are received and verified. The receiving device then discards the CRC2s to reconstitute the original block. The receiving device then deduces CRC1 and compares it with the CRC1 appended to the block. If valid, the block is accepted, and if not, the procedure is repeated.