2. Serial RapidIO Interface > Multicast Event Control Symbols
56
Tsi578 User Manual
June 6, 2016
Integrated Device Technology
www.idt.com
2.5.2
Generating an MCS
The Tsi578 supports the generation of an MCS in two ways. The first method is called the
software
usage model
which use of a maintenance write transaction in a port (see
Multicast-Event Control Symbol Register” on page 322
). The write operation to this port does not
complete — that is, no response is sent — until the MCS is enqueued for transmission. Subsequent
writes to the register are ignored until the MCS is transmitted. A register write can also be performed
from both JTAG and I
2
C.
The Tsi578 also supports a
hardware usage model
, which generates an MCS using the MCES pin as an
input. When enabled, a transition on the MCES pin signals all ports that a request to transmit an MCS
is received. All ports enabled to forward multicast control symbols then transmit an MCS (see
“RapidIO Serial Port x Control CSR” on page 281
). The minimum time between two transitions on the
MCES pin is 1
s. For example, when the host needs to create a “
heartbeat
” for the entire system at
125kHz, it should use a 62.5kHz clock to generate the pulse driving the MCES pin.
2.5.3
Restrictions
Only one port on the Tsi578 should be assigned to receive Multicast-Event control symbols.
MCES_CTRL setting should be completed before traffic starts. Changing the MCES_CTRL
setting during operation can result in the transmission of spurious MCES.
If multiple ports receive Multicast-Event control symbols closely spaced in time, or if a single
port receives multicast control symbols spaced closely in time, only one control symbol is
forwarded correctly. The other control symbols are discarded. The minimum separation
between MCS is the time, on the port with the lowest possible aggregate baud rate, to send at
least 64 code groups. The 64 code groups is taken from the lowest clock speed (port rate) in
the system.