Appendix B: Registers
143
NBCFG (Neighbour configuration)
5:0 Input delay As the serial link speed from the neighbouring slave device in
a daisy chain runs at the same speed as the serial link clock on the master
device, there is no faster clock available which can be used for oversampling
the input. So to avoid metastability on the input a delay chain is provided to
encompass this. The delay is process dependent, but in most cases, only an
approximate delay is needed which leaves room for the process variations.
The delay can be changed with a selection of ca. 0.2 ns up to ca. 12.5 ns,
which amounts to a full cycle at the minimum designed for serial link clock
speed of 80 MHz.
7:6 Neighbour priority Sets the priority of the neighbour input data in relation
to the internal data. It should be set to the number of devices following the
current device in the chain. If it is the first device in the chain and there are
two following, it should be set to two. If it is the second device in the chain
and there is one following, it should be set to one, etc. If the value is set to
two, then the device will take two packets from the neighbouring link for
each packet it takes from any of the internal channels. Only serial link 0 can
output data from the neighbouring link.
SOCFG (Serial out configuration)
3:0 Active links Sets the number of active serial link outputs. The links are activated in sequential order, setting the value to 0 disables all links. Disabling
a link also disables its corresponding driver to save power. See Table B.4
for which channel would be connected to which link when this setting is
changed.
4 Input termination The physical connections to the input SLVS links are
assumed to be differential transmission lines with a differential impedance
of 100 . The receivers have a common built-in 100 terminations, which
can be enabled if required.
5 NBflowstop_in enable The NBflowstop_in pin should be pulled low if not
in use. Setting this bit to zero will set the pin to zero internally so that serial
outputs will work normally in case the pin externally is stuck at one.
SODRVST (Serial out drive strength) The serial link drivers have a programmable
output current. This enables power saving when transmitting over short distances
or it provides the possibility to compensate for the loss in long cables. The
configurations are listed in Table B.5.
CMD:LINKSYNC (Link sync) Forces sending of a sync packet on all active links
after the current transmission on the link has completed.
B.1.7 Data Compression
Several methods of compressing the data stream before transmission is available. If
no method is selected it defaults to zero suppression. In case more than one method
is selected, the priority is raw > Huffman > cluster sum > zero suppression.
143
NBCFG (Neighbour configuration)
5:0 Input delay As the serial link speed from the neighbouring slave device in
a daisy chain runs at the same speed as the serial link clock on the master
device, there is no faster clock available which can be used for oversampling
the input. So to avoid metastability on the input a delay chain is provided to
encompass this. The delay is process dependent, but in most cases, only an
approximate delay is needed which leaves room for the process variations.
The delay can be changed with a selection of ca. 0.2 ns up to ca. 12.5 ns,
which amounts to a full cycle at the minimum designed for serial link clock
speed of 80 MHz.
7:6 Neighbour priority Sets the priority of the neighbour input data in relation
to the internal data. It should be set to the number of devices following the
current device in the chain. If it is the first device in the chain and there are
two following, it should be set to two. If it is the second device in the chain
and there is one following, it should be set to one, etc. If the value is set to
two, then the device will take two packets from the neighbouring link for
each packet it takes from any of the internal channels. Only serial link 0 can
output data from the neighbouring link.
SOCFG (Serial out configuration)
3:0 Active links Sets the number of active serial link outputs. The links are activated in sequential order, setting the value to 0 disables all links. Disabling
a link also disables its corresponding driver to save power. See Table B.4
for which channel would be connected to which link when this setting is
changed.
4 Input termination The physical connections to the input SLVS links are
assumed to be differential transmission lines with a differential impedance
of 100 . The receivers have a common built-in 100 terminations, which
can be enabled if required.
5 NBflowstop_in enable The NBflowstop_in pin should be pulled low if not
in use. Setting this bit to zero will set the pin to zero internally so that serial
outputs will work normally in case the pin externally is stuck at one.
SODRVST (Serial out drive strength) The serial link drivers have a programmable
output current. This enables power saving when transmitting over short distances
or it provides the possibility to compensate for the loss in long cables. The
configurations are listed in Table B.5.
CMD:LINKSYNC (Link sync) Forces sending of a sync packet on all active links
after the current transmission on the link has completed.
B.1.7 Data Compression
Several methods of compressing the data stream before transmission is available. If
no method is selected it defaults to zero suppression. In case more than one method
is selected, the priority is raw > Huffman > cluster sum > zero suppression.