
MOTOROLA
Chapter 6. System Configuration and Protection
6-27
System Configuration and Protection Registers
Table 6-7. SIUMCR Bit Descriptions
Bit(s)
Name
Description
0
EARB
External arbitration
0 Internal arbitration is performed
1 External arbitration is assumed
1:3
EARP
External arbitration request priority. This field defines the priority of an external master’s
4:7
—
Reserved
8
DSHW
Data show cycles. This bit selects the show cycle mode to be applied to U-bus data cycles (data
cycles to IMB modules and flash EEPROM). This field is locked by the DLK bit. Note that
instruction show cycles are programmed in the ICTRL and L-bus data show cycles are
programmed in the L2UMCR.
0 Disable show cycles for all internal data cycles
1 Show address and data of all internal data cycles
9:10
DBGC
11
DBPC
Reserved. 1
12
ATWC
Address write type enable configuration. This bit configures the pins to function as byte write
enables or address types for debugging purposes.
0WE[0:3]/BE[0:3]/AT[0:3] functions as WE[0:3]/BE[0:3] 2
1WE[0:3]/BE[0:3]/AT[0:3] functions as AT[0:3]
13:14
GPC
This bit configures the pins as shown in
Table 6-915
DLK
Debug register lock
0 Normal operation
1 SIUMCR is locked and can be written only in test mode or when the internal freeze signal is
asserted.
16
—
Reserved
17:18
SC
Single-chip select. This field configures the functionality of the address and data buses.
Changing the SC field while external accesses are performed is not supported. Refer to
19
RCTX
Reset configuration/timer expired. During reset the RSTCONF/TEXP pin functions as
RSTCONF. After reset the pin can be configured to function as TEXP, the timer expired signal
that supports the low-power modes.
0 RSTCONF/TEXP functions as RSTCONF
1 RSTCONF/TEXP functions as TEXP
20:21
MLRC
Multi-level reservation control. This field selects between the functionality of the reservation logic
22:23
—
Reserved
24
MTSC
Memory transfer start control.
0IRQ[2]/CR/SGPIOC[2]/MTS functions according to the MLRC bits setting
1IRQ[2]/CR/SGPIOC[2]/MTS functions as MTS
25
NOSHOW Instruction show cycles disabled—If the NOSHOW bit is set (1), then all instruction show cycles
are NOT transmitted to the external bus.
26
EICEN
Enhanced interrupt controller enable.
0 Enhanced interrupt controller operates in regular mode (compatible with MPC555/MPC556)
1 Enhanced interrupt controller is enabled