Transport Layer - Texas Instruments SimpleLink CC2620 Technical Reference Manual

Bootloader Interfaces
Acknowledge (ACK) bytes are sent out whenever a packet is successfully received and verified by the
receiver. A not-acknowledge (NAK) byte is sent out whenever a sent packet is detected to have an error,
usually as a result of a checksum error or just malformed data in the packet, which allows the sender to
retransmit the previous packet.
To illustrate packet handling, the basic packet format is shown in
In Figure 8-2, the top line shows the device that is transmitting data; the bottom line is the response from
the other device.
In this case, a 6-byte packet is sent with the data shown in
0x48+0x6f+0x6c+0x61 which, when truncated to 8 bits, is 0x84. The first byte transmitted holds the size of
the packet in number of bytes. Then the checksum byte is transmitted. The next bytes to go out are the 4
data bytes in this packet. The transmitter is allowed to send zeros until a nonzero response is received,
that is necessary for SSI and is allowed by the UART. The receiver is allowed to return zeros until it is
ready to ACK or NAK the packet that is being sent. Neither device transfers a nonzero byte until it has
received a response after transmitting a packet.
size
0x06
8.2.1.1 Packet Acknowledge and Not-Acknowledge Bytes
Table 8-1 shows the defined values for packet acknowledge (ACK) and not-acknowledge (NAK) bytes.

8.2.2 Transport Layer

The bootloader supports updating through the UART0 and SSI0 ports, which are available on the CC26xx
and CC13xx devices. The SSI0 port has the advantage of supporting higher and more flexible data rates,
but it also requires more connections to the CC26xx and CC13xx devices. The UART0 has the
disadvantage of having slightly lower and possibly less flexible rates. However, the UART0 requires fewer
pins and can be easily implemented with any standard UART connection.
676
Bootloader
Figure 8-2. Serial Bus Packet Format
checksum
0x84 0x48 0x6f
Table 8-1. Protocol Acknowledge/Not-Acknowledge
Protocol Byte
ACK
NACK
Copyright © 2015, Texas Instruments Incorporated
Figure
Figure 8-2. This data results in a checksum of
data
0x6c 0x61 0x00
0x00
Bytes
Value
0×CC
0×33
SWCU117C – February 2015 – Revised September 2015
www.ti.com
8-2.
0x03
ACK
0xcc
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