Control Register File
CPU Data Paths and Control
2-8
SPRU733
2.7.1 Register Addresses for Accessing the Control Registers
Table 2
−
4 lists the register addresses for accessing the control register file.
One unit (.S2) can read from and write to the control register file. Each control
register is accessed by the
MVC
instruction. See the
MVC
instruction descrip-
tion, page 3-180, for information on how to use this instruction.
Additionally, some of the control register bits are specially accessed in other
ways. For example, arrival of a maskable interrupt on an external interrupt pin,
INT
m
, triggers the setting of flag bit IFR
m
. Subsequently, when that interrupt
is processed, this triggers the clearing of IFR
m
and the clearing of the global
interrupt enable bit, GIE. Finally, when that interrupt processing is complete,
the
B IRP
instruction in the interrupt service routine restores the pre-interrupt
value of the GIE. Similarly, saturating instructions like
SADD
set the SAT
(saturation) bit in the control status register (CSR).
Table 2
−
4. Register Addresses for Accessing the Control Registers
Acronym
Register Name
Address
Read/ Write
AMR
Addressing mode register
00000
R, W
CSR
Control status register
00001
R, W
FADCR
Floating-point adder configuration
10010
R, W
FAUCR
Floating-point auxiliary configuration
10011
R, W
FMCR
Floating-point multiplier configuration
10100
R, W
ICR
Interrupt clear register
00011
W
IER
Interrupt enable register
00100
R, W
IFR
Interrupt flag register
00010
R
IRP
Interrupt return pointer
00110
R, W
ISR
Interrupt set register
00010
W
ISTP
Interrupt service table pointer
00101
R, W
NRP
Nonmaskable interrupt return pointer
00111
R, W
PCE1
Program counter, E1 phase
10000
R
Legend:
R = Readable by the
MVC
instruction; W = Writeable by the
MVC
instruction