mt90503 Zarlink Semiconductor, mt90503 Datasheet - Page 61

• Manufacturer Part Number: mt90503
• Description: 2048vc Aal1 Sar
• Manufacturer: Zarlink Semiconductor

The number of events per frame in the scheduler, Num Env, determines how much memory is allocated for each
frame in the scheduler: 2 words per event. Within this memory, the scheduler will read only the first 2m events, as
stored in the Read 2m Events field. Of the events that are read, only those with the Scheduler Num not equal to
‘1111’ (see Table 19) are executed. No action is taken on events that are read whose Scheduler Num is ’1111’.
4.3.2.4
Table 19 - Scheduler Event Fields provides a description of the fields for the transmit event scheduler entries.
Figure 24 - Transmit Event Scheduler Process to locate the fields
4.3.2.5
The maximum number of events per frame corresponds to the maximum number of events that can occur in one
frame of all the schedulers simultaneously.
If the frames are not synchronised (as in Figure 25 - Unsyncrhonised Schedulers), the maximum number of events
per frame is the sum of the maximum events in any frame of each scheduler (in this case, 32 events + 21 events =
53 events is the maximum number of events per frame). If the schedulers are synchronised (as in Figure 26 -
Synchronised Schedulers), the maximum number of events per frame is the worst in any particular frame (in this
case, 23 + 17 = 40 events is greater than 6 + 24 = 30 events, so 40 events is the maximum number). If the
schedulers are partially synchronised (as in Figure 27 - Partially Synchronised Schedulers), the maximum number
of events per frame is the worst in any frame that can possibly align (in this case, 20 + 5 = 25 events is less than 27
+ 12 = 39 events which is greater than 20 + 16 = 36 events and 27 + 7 = 34 events so 39 events is the maximum
number).
Scheduler Num
S
TX Structure
Address Pointer
Field
Scheduler Events Fields Description
Table 20 - Maximum number of Events per Frame for Common Transmission Speeds
Bandwidth Limitations for Transmit Scheduler Events
Transmit Event
Scheduler
Number
Start Bit
TX Structure
Address Pointer
Name of Field
Transmission Speed
155 Mbps
622 Mbps
25 Mbps
Table 19 - Scheduler Event Fields
+2/b14:b0
+0/b5:b2
+0/b0
Used
Bits
Zarlink Semiconductor Inc.
MT90503
This field contains the scheduler number.
0000 to 1110 = valid scheduler numbers
1111 = invalid event. No action will be taken on this event
The transmit event schedulers are read sequentially.
This field indicates the first event that will be carried out
when the VC is initialised.
Software must set the S bit of only one event once
programming of the scheduler is complete.
This bit is only relevant until the I bit is set in the TX Control
Structure. After the I bit is set, all events with valid scheduler
numbers will be executed as they are encountered.
This field is the pointer to the TX_SAR Structure used to
assemble an ATM cell each time this event is read. This field
is appended with "00000" as the LSBs to form a 20-bit
address.
61
Maximum Number of Events per Frame
Description of Field
183
45
7
Data Sheet