PXB4330 Datasheet, PDF (60/201 Pages) Infineon Technologies AG – ICs for Communications

PXB 4330
Operational Description
4.10
Empty Cell Rate Calculation Example
The internal SDRAM refresh generator uses empty cell cycles to perform its refresh cy-
cles. Thus the refresh function is closely related to the scheduler output rate
configuration. The empty cell rate generator guarantees a minimum number of empty
cell cycles required for refresh cycles. A maximum value for parameter T can be derived
by the following term:
T_max = -^S----^Y----^S-₃---₂-^C----_×^L----^K-_R----_e-^×---_f-^R-_r--_e--^e--_s--^f-_h-^r--^e-_C---^s--_y-^h--_c--^P--_l-_e-^e---_s-^r--ⁱ--^o----^d-
(8)
with:
• ABM core clock SYSCLK = [1/s]
• SDRAM RefreshPeriod = [s]
• SDRAM RefreshCycles requirement
The empty cell rate parameter definition for fractional and integer parts of T is according
to equations (5) and (6).
Example:
Given values: RefreshPeriod = 64ms, RefreshCycles = 4096, SYSCLK = 50 MHz
⇒ T_max = 24.414
Thus the value of T that is represented by programmed device parameters IntRate and
FracRate according to equations (6) and (7), must be less or equal to T_max to guarantee
sufficient refresh cycles according to the SDRAM specification.
In case of additional bandwidth needs to be reserved (e.g. for multicast operation in sub-
sequent devices), a second maximum condition for parameter T can be derived
depending on the empty cell rate required for multicast bandwidth reservation. In this
case the value of T must conform the following equation:
T = Min{T_equation(5), T_{MCreservation},T_max}
(9)
4.11
Traffic Classes
4.11.1 CBR Connections
These connections should use the real-time bypass of the respective Scheduler. How-
ever, if two priority levels for real-time connections must be offered, a slightly lower real-
time performance can be achieved by using the WFQ Multiplexer with maximum weight.
Data Sheet
4-60
09.99