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7743A–AERO–07/07

5.

Operating Modes

5.1

Configuration of the AT7912E

The AT7912E provides registers and ports for configuration. Each register contains

exactly one byte (read / write), whereas a port (e.g. a FIFO interface) behaves like a

FIFO, meaning that multiple data bytes can be read or written from/to the port.

The ports of the AT7912E such as the FIFO, UART, ADC and RAM interfaces are

accessed by a read/write command to the corresponding port address. In the case of

FIFO, Host, UART and memory interfaces, a packet oriented access is also possible

(meaning transferring multiple data bytes with a single command). The read/write selec-

tion of a command is done by setting bit 7 (MSB) of the first byte to one (read) or zero

(write).

All internal registers are 8-bit wide addressable. Two simple commands, read and write,

suffice to access all registers of the AT7912E.

Configuration/Programming of the AT7912E internal registers is done via either a simple

protocol over the SpaceWire link or STUP over the SpaceWire link or directly via the

host interface.

• The simple protocol over the SpaceWire, compatible with the T7906 (SCMCS116)

link requires a command byte and, if necessary, one or more data bytes. The simple

protocol ignores following bytes, if more bytes are sent.

• The STUP over the SpaceWire link uses 4 bytes for commands. It also supports

logical addressing.

• The host interface provides a direct access to the internal registers through a 8-bit

multiplexed address/data bus. After reset, the host interface is enabled.

After a chip reset the AT7912E is configured via the internal controller. This can be

either by receiving the configuration data from the SpaceWire link or by an external con-

troller connected to the host port of the AT7912E.