2 - Installation
Hardware Handshake
The
1.When the input buffer is full (approximately 100 characters have been received), it will set DTR false. When enough characters have been removed to make space in the input buffer, DTR will be set to true, unless condition 2 (see below) prevents this.
2.When the ac source wants to "talk", which means that it has processed a query, and has seen a <newline> message terminator, it will set DTR false. This implies that once a query has been sent to the power source, the bus controller should read the response before attempting to send more data. It also means that a <newline> must terminate the command string. After the response has been output, the ac source will set DTR true again, unless condition #1 prevents this.
The ac source monitors the DSR (data set ready) line to determine when the bus controller is ready to accept data. It checks this line before each character is sent, and the output is suspended if DSR is false. When DSR goes true, transmission will resume. The ac source will leave DTR false while output is suspended. A form of deadlock exists until the bus controller asserts DSR true to allow the ac source to complete the transmission.
Null modem
bus controller | ac source |
TxD (3) | TxD (3) |
RxD (2) | RxD (2) |
*DTR (4) | DTR (4) |
*DSR (6) | DSR (6) |
Ground (5) | Ground (5) |
|
|
Figure 2-7. Null Modem Interface Lines
Response Data Terminator
All
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