Age Count Threshold Register (Age_Cnt_Thresh)—Non-Ehci - Freescale Semiconductor MPC8313E Family Reference Manual

Universal Serial Bus Interface
Table 16-33 describes the SNOOPn register fields.
Bits Name
0–19 Snoop address
20–26 —
27–31 Snoop Enables
16.3.2.25 Age Count Threshold Register (AGE_CNT_THRESH)—Non-EHCI
Note that this register uses big-endian byte ordering and is not defined in the EHCI specification. The age
count threshold (AGE_CNT_THRESH) register provides the aging counter threshold value used to
determine the priority state of the USB DR controller's internal system interface. This is used to increase
the priority state of the module's system interface from zero to one. The actual priority level on the system
bus for each state is defined by the PRI_CTRL register. See
PRIORITY[0:1]," for more details on bus priority. The threshold value is in units of csb_clk cycles. This
register should be written during system initialization or during normal system operation when the system
bus interface is idle. It can be read at any time.
If the aging counter is less than the AGE_CNT_THRESH value, priority state zero is chosen. If the aging
counter is greater than or equal to the AGE_CNT_THRESH value, priority state one is chosen.
The aging counter begins to count from zero when a bus access is requested. It increments every bus cycle
until the bus transaction completes. At the completion of a bus transaction, the counter is synchronously
reset to zero. If there are any outstanding bus requests, the aging counter will then begin counting
immediately.
The AGE_CNT_THRESH is compared against the value of the aging counter during each clock cycle of
the current transaction. If AGE_CNT_THRESH is equal to zero, priority state one is always chosen. If the
MPC8313E PowerQUICC II Pro Integrated Processor Family Reference Manual, Rev. 3
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Table 16-33. SNOOP n Register Field Descriptions
The starting base address for which transactions are snooped.
Reserved, should be cleared
0x00 Snooping disabled
0x0B 4-Kbyte snoop range starting at the value defined by SNOOP n [0–19]
0x0C 8-Kbyte snoop range starting at the value defined by SNOOP n [0–18]
0x0D 16-Kbyte snoop range starting at the value defined by SNOOP n [0–17]
0x0E 32-Kbyte snoop range starting at the value defined by SNOOP n [0–16]
0x0F 64-Kbyte snoop range starting at the value defined by SNOOP n [0–15]
0x10 128-Kbyte snoop range starting at the value defined by SNOOP n [0–14]
0x11 256-Kbyte snoop range starting at the value defined by SNOOP n [0–13]
0x12 512-Kbyte snoop range starting at the value defined by SNOOP n [0–12]
0x13 1-Mbyte snoop range starting at the value defined by SNOOP n [0–11]
0x14 2-Mbyte snoop range starting at the value defined by SNOOP n [0–10]
0x15 4-Mbyte snoop range starting at the value defined by SNOOP n [0–9]
0x16 8-Mbyte snoop range starting at the value defined by SNOOP n [0–8]
0x17 16-Mbyte snoop range starting at the value defined by SNOOP n [0–7]
0x18 32-Mbyte snoop range starting at the value defined by SNOOP n [0–6]
0x19 64-M byte snoop range starting at the value defined by SNOOP n [0–5]
0x1A 31-Mbyte snoop range starting at the value defined by SNOOP n [0–4]
0x1B 256-Mbyte snoop range starting at the value defined by SNOOP n [0–3]
0x1C 512-Mbyte snoop range starting at the value defined by SNOOP n [0–2]
0x1D 1-Gbyte snoop range starting at the value defined by SNOOP n [0–1]
0x1E 2-Gbyte snoop range starting at the value defined by SNOOP n [0]
Description
Section 6.3.1.1, "Address Bus Arbitration with
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