mt90870ag2 Zarlink Semiconductor, mt90870ag2 Datasheet - Page 50

• Manufacturer Part Number: mt90870ag2
• Description: Flexible 12 K Digital Switch F12kdx
• Manufacturer: Zarlink Semiconductor

12.4
The Backplane Connection Memory (BCM) has 8,192 addresses of 16-bit words. Each address, accessed through
bits A13-A0 of the microprocessor port, is allocated to an individual Backplane output stream and channel. The bit
definition for each 16-bit word is presented in Table 13 for Local-to- Backplane (Non-32 Mb/s Mode) and
Backplane-to-Backplane (Non-32 Mb/s Mode) connections, and in Table 14, for Local-to-Backplane (32 Mb/s
Mode) and Backplane-to-Backplane (32 Mb/s Mode) connections.
Bit BSRC selects the switch configuration for Local-to-Backplane or Backplane-to-Backplane. When the per-
channel Message Mode is selected (BMM = HIGH), the lower byte of the BCM word (BCAB7-0) will be transmitted
as data on the output stream (BSTo0-31) in place of data defined by the Source Control, Stream Address and
Channel Address bits.
12-9
12-8
7-0
Bit
Bit
15
14
13
15
14
13
Backplane Connection Memory Bit Definition
BSAB3-0
BSAB4-0
BCAB7-0
BSRC
Name
BSRC
Name
BMM
Table 13 - BCM Bits for Local-to-Backplane and Backplane-to-Backplane Switching
BMM
BE
BE
Backplane Source Control Bit.
When LOW, the source is from the Local input port (Local Data Memory).
When HIGH, the source is from the Backplane input port (Backplane Data Memory).
BSRC is ignored when BMM is set HIGH in Message Mode.
Backplane Message Mode Bit.
When LOW, the channel is in Connection Mode.
When HIGH, the channel is in Message Mode.
Backplane Output Enable Bit.
When this bit is low the channel may be high impedance, either at the device output or set
by an external buffer, dependent upon the BORS pin. When the bit is high the channel is
active.
Backplane Source Stream Address Bits.
The binary value of these 4 bits represents the input stream number.
BSAB3-0 are ignored when BMM is set HIGH in Message Mode.
Backplane Source Control Bit.
When LOW, the source is from the Local input port (Local Data Memory). When HIGH, the
source is from the Backplane input port (Backplane Data Memory).
Ignored when BMM is set HIGH.
Backplane Message Mode Bit.
When LOW, the channel is in Connection Mode. When HIGH, the channel is in Message
Mode.
Backplane Output Enable Bit.
When LOW the channel may be high impedance, either at the device output or set by an
external buffer, dependent upon the BORS pin. When HIGH the channel is active.
Backplane Source Stream Address Bits.
The binary value of these 5 bits represents the input stream number. BSAB4-0 are ignored
when BMM is set HIGH in Message Mode.
Source Channel Address Bits.
The binary value of these 8 bits represents the input channel number when BMM is set
LOW. BCAB7-0 are transmitted as data when BMM is set HIGH in Message Mode.
(Non-32 Mb/s Mode)
Zarlink Semiconductor Inc.
MT90870
50
Description
Description
Data Sheet