System Control Module (SCM)
MCF52235 ColdFire® Integrated Microcontroller Reference Manual, Rev. 6
13-12
Freescale Semiconductor
The initial state of the master priorities is M3 > M2 > M1 > M0. System software should guarantee that
the programmed M
n
_PRTY fields are unique, otherwise the hardware defaults to the initial-state priorities.
NOTE
The M1_PRTY field should not be set for a priority higher than third
(default).
13.7
System Access Control Unit (SACU)
This section details the functionality of the system access control unit (SACU), which provides the
mechanism needed to implement secure bus transactions to the address space mapped to the internal
modules.
13.7.1
Overview
The SACU supports the traditional model of two privilege levels: supervisor and user. Typically, memory
references with the supervisor attribute have total accessibility to all the resources in the system, while user
mode references cannot access system control and configuration registers. In many systems, the operating
system executes in supervisor mode, while application software executes in user mode.
21–20
M2_PRTY
Master priority level for master 2 (DMA Controller)
00 Fourth (lowest) priority
01 Third priority
10 Second priority
11 First (highest) priority
19–18
M0_PRTY
Master priority level for master 0 (ColdFire Core)
00 Fourth (lowest) priority
01 Third priority
10 Second priority
11 First (highest) priority
17–15
Reserved, should be cleared.
14
FIXED
Fixed or round robin arbitration
0 Round robin arbitration
1 Fixed arbitration
13
TIMEOUT
Timeout Enable
0 Disable count for when a master is locked out by other masters.
1 Enable count for when a master is locked out by other masters and allow access when LCKOUT_TIME is
reached.
12
PRKLAST
Park on the last active master or highest priority master if no masters are active
0 Park on last active master
1 Park on highest priority master
11–8
LCKOUT_TIME
Lock-out Time. Lock-out time for a master being denied the bus.
The lock out time is defined as 2^ LCKOUT_TIME[3:0].
7–0
Reserved, should be cleared.
Table 13-6. MPARK Field Descriptions (continued)
Field
Description
Because
of
an
order
from
the
United
States
International
Trade
Commission,
BGA-packaged
product
lines
and
part
numbers
indicated
here
currently
are
not
available
from
Freescale
for
import
or
sale
in
the
United
States
prior
to
September
2010:MCF52234CVM60,
MCF52235CVM60