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3-3. Data Transaction Sequencing and Timing Requirements
3-3-1. Data Packet Transaction Sequencing Requirements
The RT-20/Host Data Packet Transactions can be described in one of the three following sequences:
•
The HOST sends a command data packet and the RT-20 responds with an ACK or a NAK data packet.
•
The HOST sends a status request data packet and the RT-20 responds with the corresponding status
data packet or NAK if the request is invalid.
•
The RT-20 sends an auto status feedback data packet if the corresponding RT-20 status has changed
(The HOST is not required to respond to the RT-20).
3-3-2. Data Transaction Timing Requirements
Each of the HOST/RT-20 data transactions must meet the following timing requirements:
•
Response packet transmission (ACK, NAK or Status) from the RT-20 will be initiated approximately within
50ms following the end of the HOST command packet and transmission will be completed within 500ms
following the end of the HOST command packet.
•
The HOST should not transmit a command or status request data packet until the RT-20 has responded to
the previously sent command. A new command or status request data packet may be initiated if the RT-20
has been unresponsive for at least 1s.
•
The RT-20 will complete an auto status feedback data packet within 500ms.
3-3-3. Specific Requirements for Auto Status Feedback
The following items detail specific requirements for the Auto Status Feedback data transactions.
The RT-20 Auto Status Feedback has been grouped into three layers: 1, 2 and 3:
•
Layer 1 is the highest priority status. Layer 2 is the second highest priority. Layer 3 is assigned the lowest
priority.
•
Each layer is independently enabled or disabled by the HOST. The RT-20 will disable all three layers by
default.
•
The RT-20 initiates the Auto Status Feedback transaction when the corresponding RT-20 status has
changed.
3-3-4. Example of the transactions
HOST RT-20
TxD RxD
RxD TxD
Example Data Packet Transactions
max. 0.5sec
a transaction
a transaction
Command
ACK or NAK
Status request
Status
max. 0.5sec
