Nevion FR202 - Manual (Page 28)

FR-2RU-20-2 Rev. A
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7
Flashlink control protocol
7.1 Document conventions
All commands sent to the card are printed in italics.
This is a command sent to a card.
All responses sent from a card to the controller are printed in bold.
This is a response sent from a card to the controller.
7.2 Hardware interface
The hardware interface is basically RS-422, a serial communication standard much like RS-
232 but with balanced lines. You can use a simple (dumb) RS-232 to RS-422 converter if
you want to use a standard RS-232 port (eg. a PC COM port).
The receive and transmit lines can be connected to make a true RS-485 bus, but this
requires special care from the PC side, since you have to control the bus direction (e.g.
using a dedicated RS-485 board with RS-485 drivers). We recommend using RS-422 for
control.
Data rate: 115200 bps, 8 bits, with one stop bit and no parity.
All data is 8 bit ASCII (ISO8859-1 encoding, but currently any ASCII encoding will do since
no special ASCII characters are used).
7.3 Addressing
Each card has a unique identifier called card position, which is assigned (trough hardware
pinning) automatically when a card is inserted into a subrack. The card positions are
numbered from 1 to 20 from a user point of view. From a protocol (or software) point of
view, the cards are numbered 0-19. When we refer to card position in this document, we
refer to this "low level id" numbered 0-19, but the user should always see positions 1-20 in
menus, etc.
Each frame (if you use more than one) should have a unique frame id, numbered 0-7 (user
and protocol/software wise). The id is set by rotary switches on the rear of the rack, behind
the power supply at the left side.
7.4 General command structure
Each command is built up of a sequence of ASCII characters terminated by linefeed. The
first two characters are the source address (source frame id and the source card position).
Frame structure:
Byte 0 Rack ID (0-7); Destination
Byte 1 Card position (0-19); Destination
Byte 2 Rack ID (0-7); Source
Byte 3 Card position (0-19); Source
Byte 4
– n
Command or command response
Byte n+1 Linefeed (10 decimal, 0x0A hex)
If the command or command response contains a line feed, it is preceded by a backslash
(\).
7.5 Card detection (hot swap)
The controller must send a "hello" command to gain control over a board, this is to make
sure that the control software is aware of any card changes. After a power up or hot swap,
the card does not respond to any other command than hello.