mcf5407 Freescale Semiconductor, Inc, mcf5407 Datasheet - Page 225

• Manufacturer Part Number: mcf5407
• Description: Mcf5407 Coldfire Integrated Microprocessor User
• Manufacturer: Freescale Semiconductor, Inc

6.2.10 Bus Arbitration Control
This section describes the bus arbitration register and the four arbitration schemes.
6.2.10.1 Default Bus Master Park Register (MPARK)
The MPARK, shown in Figure 6-9, determines the default bus master arbitration between
internal transfers (core and DMA module) and between internal and external transfers to
internal resources. This arbitration is needed because external masters can access internal
registers within the MCF5407 peripherals.
Table 6-6 describes MPARK bits.
Address
Bits
7–6
5
4
Reset
Field
R/W
EARBCTRL External bus arbitration control. Enables internal register memory space to external bus
IARBCTRL
Name
PARK
7
PARK
Figure 6-9. Default Bus Master Register (MPARK)
Park. Indicates the arbitration priority of internal transfers among MCF5407 resources.
00 Round-robin between DMA and ColdFire core
01 Park on master ColdFire core
10 Park on master DMA module
11 Park on current master
Use of this field is described in detail in Section 6.2.10.1.1, “Arbitration for Internally
Generated Transfers (MPARK[PARK]).”
Internal bus arbitration control. Controls external device access to the MCF5407 internal bus.
0 Arbitration disabled (single-master system)
1 Arbitration enabled. IARBCTRL must be set if external masters are using internal
Use of this bit depends on whether the system has single or multiple masters, as follows:
arbitration. Internal registers are those accessed at offsets to the MBAR. These include the
SIM, DMA, chip selects, timers, UARTs, I
not include the MBAR; only the core can access the MBAR.
0 Arbitration disabled
1 Arbitration enabled
The use of this field is described in detail in Section 6.2.10.1.2, “Arbitration between Internal
and External Masters for Accessing Internal Resources.”
• In a single-master system, IARBCTRL should stay cleared, disabling internal arbitration
• In multiple master systems that expect to use internal resources like the DRAM controller
resources like the DRAM controller or chip selects.
by external masters. In this scenario, MPARK[PARK] applies only to priority of internal
masters over one another. Note that the internal DMA (master 3) has priority over the
ColdFire core (master 2), if internal DMA bandwidth is at its maximum (BWC = 000).
or chip selects, internal arbitration should be enabled. The external master defaults to the
highest priority internal master anytime BG is negated.
6
Table 6-6. MPARK Field Descriptions
IARBCTRL EARBCTRL SHOWDATA
5
Chapter 6. SIM Overview
4
MBAR + 0x0C
0000_0000
R/W
Description
2
C, and parallel port registers. These registers do
3
2
Programming Model
—
0
6-11