PEB22554 SIEMENS [Siemens Semiconductor Group], PEB22554 Datasheet - Page 59

• Manufacturer Part Number: PEB22554
• Description: ICs for Communications
• Manufacturer: SIEMENS [Siemens Semiconductor Group]

Transmit Elastic Buffer
The received bit stream from pin XDI is optionally stored in the transmit elastic buffer.
The memory is organized as the receive elastic buffer. The functions are also equal to
the receive side. Programming of the transmit buffer size is done by SIC1.XBS1/0 :
• XBS1/0 = 00 : Bypass of the transmit elastic buffer
• XBS1/0 = 01 : one frame buffer or 256 bits
• XBS1/0 = 10 : two frame buffer or 512 bits
• XBS1/0 = 11 : short buffer or 92 bits :
The functions of the transmit buffer are:
• Clock adaption between system clock (SCLKX) and internally generated transmit
• Compensation of input wander and jitter.
• Frame alignment between system frame and transmit route frame
• Reporting and controlling of slips
Writing of received data from XDI is controlled by SCLKX/R and SYPX / XMFS in
conjunction with the programmed offset values for the transmit time-slot/clock-slot
counters. Reading of stored data is controlled by the clock generated by DCO-X
circuitry or the externally generated TCLK and the transmit framer. With the dejittered
clock data is read from the transmit elastic buffer and are forwarded to the transmitter.
Reporting and controlling of slips is done according to the receive direction. Positive /
negative slips are reported in interrupt status bits ISR4.XSP and ISR4.XSN. If the
transmit buffer is bypassed data is directly transfered to the transmitter.
The following table gives an overview of the transmit buffer operating modes.
Semiconductor Group
Buffer Size
bypass
short buffer
1 frame
2 frames
Max. wander amplitude (peak-to-peak): 94 UI (1 UI = 488 ns )
average delay after performing a slip: 128 bits
Maximum of wander amplitude: 190 UI
average delay after performing a slip: 1 frame or 256 bits
Max. wander amplitude: 18 usec
route clock (XCLK).
average delay after performing a slip: 46 bits
enabled
enabled
enabled
TS Offset program.
enabled
59
Slip perform.
no
yes
yes
yes
Functional Description E1
PEB 22554
09.98