2.0 Circuit Description
CX28394/28395/28398
2.3 System Bus
Quad/x16/Octal—T1/E1/J1 Framers
2.3.2 Externally Multiplexed Mode
Externally Multiplexed mode allows any two, three, or four framers (in the same
or different devices) to share a common high speed system bus (see Figure 2-7).
The 4.096 and 8.192 MHz bus modes contain multiple bus members (bus groups
A, B, C, D) which allow multiple T1/E1 signals to share the same system bus.
This is done by interleaving the time slots from up to four framers (see
Figures 2-10 and 2-11).
To use Externally Multiplexed mode, SBIMODE[0] and/or SBIMODE[1] in
the Framer Control register [FCR; addr 080] must be zero to disable Internally
Multiplexed mode. 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.
Figure 2-7. Externally Multiplexed Configuration Examples
Possible Externally Multiplexed
Configurations
4.096 Mbps
8.192 Mbps
8.192 Mbps
Framer 1
Framer 2
Framer 3
Framer 4
Framer 1
Framer 2
Framer 3
Framer 4
Any 2, 3, or 4 framers from a
device (or from different
devices) can be externally
multiplexed with no additional
circuitry.
4.096 Mbps
4.096 Mbps
Framer 5
Framer 6
Framer 7
Framer 8
Framer 5
Framer 6
Framer 7
Framer 8
2.048 Mbps
1.544 Mbps
CX28398
CX28398
2-22
Conexant
100054E
CONEXANT [ CONEXANT SYSTEMS, INC ]
