General information

A hub is, like in any other network, a logical unit that merges the data coming in on different lines and sends it out on every other line.

Hub logic: Example of operation

Let's assume, we have a hub with 5 interfaces. (Whether they are media independent interfaces or application interfaces does not matter, they are all treated the same inside the hub logic). A data transmission is coming in on the init channel of line 1. This data is copied to the init channel of all other lines. Now, we have to wait for the answers on all four channels. Lines 2 and 3 react immediately with a TRM on the reply channel. These TRM are stored until all interfaces have sent their answers. Lines 4 and 5 send back some data. First the data of line 4 is passed to line 1, who initiated the transfer. After the TRM of line 4 is received, the data of line 5 is read and sent to line 1. Now all interfaces have sent their TRM, so the merged TRM of all interfaces is sent to line 1. The transfer is finished and the hub goes back to idle mode.

Configuration

Each hub can be configured by a large number of generics. The complete table can be found in TrbNetConfiguration.

Control registers

Every hub has its own network address and one slow control interface. This is used to retrieve information about the current status, to switch off unused interfaces or to solve an error condition.

Address	Direction	Name	Description
80-83	STAT	HUB_STAT_locked	1 bit per port. '1' when waiting for TRM, '0' otherwise
84	STAT	HUB_STAT_active_points	1 bit per port - '1' when link is active, '0' when link is not operational
85	CFG	HUB_UPLINKS	Lists all uplinks
86	CFG	HUB_DOWNLINKS	Lists all downlinks
87	STAT	IPU_STATUS	IPU status register
88-8B	STAT	HUB_STAT_TIMEOUT	timeout of a connected endpoint, one register for each channel. Status is cleared after read
8C-8F	STAT	HUB_STAT_ACK	status for all init obufs: set if obuf is waiting for two acknowledges
90-9F	STAT	HUB_ERROR_BITS	0-7:LVL1 0-7, 8-15:LVL1 23-16, 16-23:IPU 0-7, 24-31:IPU 23-16
A0-A3	STAT	HUB_STAT_ERROR	status & error bits per channel
A4	STAT	HUB_SCTRL_ERROR	combination of errorbits 1,3,6 in slow control channel per port

Address	Direction	Name	Description
C0	CTRL	HUB_CTRL_SWITCH_PORTS_CH0	Switch port logically off on channel 0
C1	CTRL	HUB_CTRL_SWITCH_PORTS_CH1	see above
C2	CTRL	HUB_CTRL_SWITCH_PORTS_CH2	see above
C3	CTRL	HUB_CTRL_SWITCH_PORTS_CH3	see above
C4	CTRL	HUB_CTRL_SWITCH_INTERFACE	completely switch off port (currently: Do NOT use)
C5	CTRL	HUB_TIMEOUT_TIME	set timeout delay for each channel (4 bits per channel) *
C6	CTRL	LOCAL_NETWORK_RESET	reset part of network connected to this link

*)Timeout time is a 4 bit value which determines the time the downlink has to answer until a timeout occurs. Time = (2**(value+16))/Clock_freq = 0.66ms * 2**value. 0 switches timeout off.