MPC5553/MPC5554 Microcontroller Reference Manual, Rev. 5
7-6 Freescale Semiconductor
7.2.1.2 Slave General-Purpose Control Registers (XBAR_SGPCRn)
The XBAR_SGPCRn of a slave port controls several features of the slave port, including the following:
• Round-robin or fixed arbitration policy for a particular slave port
• Write protection of any slave port registers
• Parking algorithm used for a slave port
The PARK field indicates which master port this slave port will park on when no active access attempts
are being made to the slave and the parking control field is set to park on a specific master.
XBAR_SGPCRn[PARK] should only be programmed to select master ports that are actually available on
the device, otherwise undefined behavior will result. The low-power park feature can result in an overall
power savings if the slave port is not saturated; however, an extra clock of latency will result whenever
any master tries to access a slave (not being accessed by another master) because it will not be parked on
any master.
The XBAR_SGPCR can only be accessed in supervisor mode with 32-bit accesses. After the RO (read
only) bit has been set in the XBAR_SGPCR, the XBAR_SGPCR and the SBAR_MPR can only be read.
Attempts to write to them will have no effect and will result in an error response.
26–27 MSTR1 Master 1 priority. Set the arbitration priority for master port 1 on the associated slave port.
00 This master has the highest priority when accessing the slave port.
01 This master has the 2nd highest priority when accessing the slave port
10 This master has the 3rd highest priority when accessing the slave port.
11 This master has the lowest priority when accessing the slave port.
28–29 — Reserved, should be cleared.
30–31 MSTR0 00 This master has the highest priority when accessing the slave port.
01 This master has the 2nd highest priority when accessing the slave port
10 This master has the 3rd highest priority when accessing the slave port.
11 This master has the lowest priority when accessing the slave port.
Table 7-3. XBAR_MPRn Descriptions (Continued)
Bits Name Description
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