PXB4219 Datasheet, PDF (112/290 Pages) Infineon Technologies AG – IWE8 Interworking Element for 8 E1/T1 Lines

PXB4219 / PXB4220 / PXB4221
Interface Description
5.4
Clock Recovery Interface
It is possible to use an external device for clock recovery instead of the ICRC. Therefore
an external clock recovery interface is provided.
It allows the transmission and reception of serial communication frames containing
SRTS values or ACM buffer filling levels to and from an external clock recovery circuit.
The usage is controlled by the bits “rtsgen” and “rts_eval” in the Operation Mode
Register (“opmo”, see Chapter 7.24).
The Clock Recovery Interface is a 5 line serial interface: 1 data input SDI, 2 data outputs
SDOD and SDOR and 1 synchronization output SSP. The interface allows connection to
external clock recovery circuits. Two methods for clock recovery are supported:
Synchronous Residual Time Stamp (SRTS) and Adaptive Clock Method (ACM). The
IWE8 also allows a combination of SRTS and ACM.
The data sent over the serial lines is always formatted in frames of 32 bits.
The SSP pulse indicates the frame start for both directions. The inter-frame delay should
be equivalent to the payload of 8 ATM cells (e.g. for completely filled cells without SDT
every 3008 clock periods). Each valid frame is supposed to contain a valid RTS value
Table 27 shows the interface frame format. Bit [31] is sent first. When no data is to be
sent, idle frames are transmitted consisting of bits [31:1] all 1 and parity bit[ 0] = 0.
Table 27 also indicates which data fields are used on the different interface signals.
Table 27 Clock Recovery Interface frame format
Bits
Data field
SDI
SDOD
SDOR
31- 29
111
Yes
Yes
Yes
28 - 25
RTS[3:0]
Yes
Yes
No
24 - 11
buffer_fill[13:0]
No
Yes
No
10
RTS_valid
No
Yes
No
9-8
00
Yes
Yes
Yes
7-5
port_nr[2:0]
Yes
Yes
Yes
4-2
type[2:0]
001: RTS only
No
010: “buffer_fill” only
No
011: RTS + “buffer_fill”
No
111: reset RTS logic
No
others: not used
Yes
No
Yes
No
Yes
No
No
Yes
1
frame_invalid
Yes
Yes
Yes
0
odd_parity
Yes
Yes
Yes
Data Sheet
112
2002-05-06