cp3cn17 National Semiconductor Corporation, cp3cn17 Datasheet - Page 109

• Manufacturer Part Number: cp3cn17
• Description: Reprogrammable Connectivity Processor With Can Interface
• Manufacturer: National Semiconductor Corporation

16.6.4
The AAI can operate in a special IOM-2 compatible mode to
allow to connect to an external ISDN controller device. In
this IOM-2 mode, the AAI can only operate as a slave, i.e.
the bit clock and frame sync signal is provided by the ISDN
controller. The AAI only supports the B1 and B2 data of the
IOM-2 channel 0, but ignores the other two IOM-2 channels.
The AAI handles the B1 and B2 data as one 16-bit data
word.
Figure 52 shows the connections between an ISDN control-
ler and a CP3CN17 using a standard IOM-2 interface for the
B1/B2 data communication and the external bus interface
(IO Expansion) for controlling the ISDN controller.
Figure 52. CP3CN17/ISDN Controller Connections
CP3CN17
IOM-2 Mode
SELIO
A[7:0]
D[7:0]
SRD
SCK
SFS
STD
RD
STD/SRD
SFS
B1
IOM-2 Channel 0
Bit Clock
Frame Sync
Data In
Data Out
Address
Data
Chip Select
Output Enable
B2
Figure 51. IOM-2 Frame Structure
ISDN Controller
M
C
DS159
IC1
IOM-2 Frame (125 µs)
IOM-2 Channel 1
109
IC2
The IOM-2 interface has the following properties:
Figure 51 shows the structure of an IOM-2 Frame.
To connect the AAI to an ISDN controller through an IOM-2
compatible interface, the AAI needs to be configured in this
way:
16.6.5
In loopback mode, the STD and SRD pins are internally
connected together, so data shifted out through the ATSR
register will be shifted into the ARSR register. This mode
may be used for development, but it also allows testing the
transmit and receive path without external circuitry, for ex-
ample during Built-In-Self-Test (BIST).
M
Bit clock of 1536 kHz (output from the ISDN controller)
Frame repetition rate of 8 ksps (output from the ISDN
controller)
Double-speed bit clock (one data bit is two bit clocks
wide)
B1 and B2 data use 8-bit log PCM format
Long frame sync pulse
The AAI must be in IOM-2 Mode (AGCR.IOM2 = 1).
The AAI operates in synchronous mode (AGCR.ASS =
0).
The AAI operates as a slave, therefore the bit clock and
frame sync source selection must be set to external
(ACGR.IEFS = 1, ACGR.IEBC = 1).
The frame sync length must be set to long frame sync
(ACGR.FSS = 1).
The data word length must be set to 16-bit (AGCR.DWL
= 1).
The AAI must be set to normal mode (AGCR.SCS[1:0] =
0).
The internal frame rate must be 8 ksps (ACCR = 00BE).
C
Loopback Mode
IOM-2 Channel 2
C
DS162
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