
System Interface Unit
MOTOROLA
MPC801 USER’S MANUAL
12-17
12
12.12 PROGRAMMING THE SYSTEM INTERFACE UNIT
12.12.1 System Configuration and Protection Registers
12.12.1.1 SIU MODULE CONFIGURATION REGISTER.
The SIU module configuration
register (SIUMCR) contains bits that configure various features of the system interface unit
module.
EARB—External Arbitration
If this bit is set (1), external arbitration is assumed. If it is cleared (0), internal arbitration is
performed. For more information, refer to
Section 13.4.6 Arbitration Phase Signals
.
EARP—External Arbitration Request Priority
This field defines the priority of the external master’s arbitration request. This field is valid
when EARB is cleared. 000 is the lowest priority level and 111 is the highest. For more
information, refer to
Section 13.4.6 Arbitration Phase Signals
.
Bits 4–7 and 13—Reserved
These bits are reserved and should be set to 0.
DSHW—Data Show Cycles
This bit selects the show cycle mode to be applied to data cycles. Instruction show cycles
are programmed in the ICTRL register. Refer to
Section 18.5.2 Development Port
Registers
for more information. This bit is locked by the DLK bit.
0 = Disable show cycles for all internal data cycles.
1 = Show address and data of all internal data cycles.
SIUMCR
BIT
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
FIELD
EARB
EARP
RESERVED
DSHW
DBGC
DBPC
RES
FRC
DLK
RESET
0
0
0
0
0
0
0
0
0
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
BIT
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
FIELD
OPAR
PNCS
DPC
MP
RE
MLRC
AEME
SEME
RES
GB5E
B2DD
B3DD
RESERVED
RESET
0
0
0
0
0
0
0
0
0
0
0
0
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W