23
© MiMOMax 2013 Four Wire Audio
Interface Manual
5.2
H
IGH
S
PEED
S
ERIAL
I
NTERCONNECT
(HSSI)
5.2.1
Overview
The High Speed Serial Interconnect is a full duplex interface with independent transmit and
receive paths. FWA firmware prior to version 3.00 has a HSSI implementation where the
clock and data are separate. Subsequent versions utilise a HSSI v2 implementation where
the clock is embedded with the data. When HSSI v2 is utilised the clock signals provided by
the physical interface are held in a static state and not used. Signalling levels over all HSSI
connections conform to RS422.
The rate of FWA interface frames from the FWA interface to the Radio Unit is 4kHz except
when no ports are active, in which case no frames are sent. Any sent frames will contain data
for all enabled ports at that time.
A single HSSI payload from a Radio Unit to the FWA interface may contain 1 or more FWA
interface frames. These contain the Audio and/or COM port data streams. The frame rate is
dependent on the air interface configuration.
422
422
422
422
8
6
3
5
1
2
7
4
Recieve Clock
Recieve Data
Transmit Clock
Transmit Data
HSSI Port
Shield
HSSI v2 Framer
FWA Data
Four Wire Audio Unit
Circuit Overview
