CX28394/28395/28398
2.0 Circuit Description
Quad/x16/Octal—T1/E1/J1 Framers
2.3 System Bus
2.3.3 Internally Multiplexed Mode
Internally Multiplexed mode operation is very similar to Externally Multiplexed
mode. The framers in each device are internally grouped into four-framer groups
to allow an internally multiplexed mode (see Figure 2-8). In the CX28398,
framers 1 through 4 form a group (lower group or group A) and framers 5 through
8 form another (upper group or group B). The CX28395 supports four groups: A,
B, C, and D. The CX28394’s four framers are also grouped in the same manner. In
this mode, system bus signals from all four framers are internally connected and
the interface pin functions are redefined. The advantage of this mode is that all
system bus signals which are normally available on dual function pins, are now
available on separate pins. In Internally Multiplexed mode, the following signals
are available for each four-framer group (lower group shown):
Receive System Bus (RSB) Transmit System Bus (TSB)
RSBCKI[A]
RPCMO[A]
RFSYNC[A]
RINDO[A]
TSBCKI[A]
TPCMI[A]
TFSYNC[A]
TINDO[A]
Common, internally
connected to all four
framers.
RSIGO[1:4]
TSIGI[1:4]
RMSYNC[1:4]
TMSYNC[1:4]
(1)
(1)
RDLCKO[1:4]
TDLCKO[1:4]
Separate signals.
(1)
(1)
RDLO[1:4]
TDLI[1:4]
SIGFRZ[1:4]
—
NOTE(S):
(1)
These signals are not provided on the CX28395.
To use Internally Multiplexed mode, SBIMODE[0] and/or SBIMODE[1] in
the Framer Control register [FCR; addr 080] must be set to 1. The system bus rate
is independent of the line rate and must be selected using SBI[3:0] in the System
Bus Interface Configuration register [SBI_CR; addr 0D0]. SBI[3:0] is also used
to assign each framer to a different bus group. Register bits SBI_OE [SBI_CR;
addr 0D0], BUS_RSB [RSB_CR; addr 0D1], and BUS_TSB [TSB_CR; addr
0D4] must be set to 1 to allow system bus outputs to share common connections.
Because RFSYNC (and TFSYNC) signals are bused, all four framers’ RFSYNC
(and TFSYNC) signals must be configured as inputs and driven externally or,
alternatively, three framers’ sync signals can be configured as inputs and one as
an output [PIO; addr 018].
100054E
Conexant
2-23
CONEXANT [ CONEXANT SYSTEMS, INC ]
