HD64F2168 Datasheet, PDF (712/874 Pages) Renesas Technology Corp – Renesas 16-Bit Single-Chip Microcomputer

(2) Bit-Rate-Adjustment State
The bit rate is calculated by measuring the period of transfer of a low-level byte (H'00) from the
host. The bit rate can be changed by the command for a new bit rate selection. After the bit rate
has been adjusted, the boot program enters the inquiry and selection state. The bit-rate-adjustment
sequence is shown in figure 20.20.
Host
H'00 (30 times maximum)
H'00 (Completion of adjustment)
H'55
H'E6 (Boot response)
(H'FF (error))
Boot Program
Measuring the
1-bit length
Figure 20.20 Bit-Rate-Adjustment Sequence
(3) Communications Protocol
After adjustment of the bit rate, the protocol for communications between the host and the boot
program is as shown below.
1. 1-byte commands and 1-byte responses
These commands and responses are comprised of a single byte. These are consists of the
inquiries and the ACK for successful completion.
2. n-byte commands or n-byte responses
These commands and responses are comprised of n bytes of data. These are selections and
responses to inquiries.
The amount of programming data is not included under this heading because it is determined
in another command.
3. Error response
The error response is a response to inquiries. It consists of an error response and an error code
and comes two bytes.
4. Programming of 128 bytes
The size is not specified in commands. The size of n is indicated in response to the
programming unit inquiry.
5. Memory read response
Rev. 3.00, 03/04, page 672 of 830