bdi
GDB
for GNU Debugger, BDI2000 (ARM)
User Manual
47
© Copyright 1997-2005 by ABATRON AG Switzerland
V 1.17
3.4.2 CP15 Registers
Via Telnet it is possible to access the Coprocessor 15 (CP15) registers. Following the two Telnet com-
mands that are used to access CP15 registers:
"RDCP <number> display control processor 15 register"
"RMCP <number> <value> modify control processor 15 register"
The parameter number selects the CP15 register. This parameter has a special numbering scheme
which depends of the ARM CPU type. More information is also found in the ARM documentation.
ARM710T, ARM720T,ARM740T:
The 16bit register number is used to build the appropriate MCR/MRC instruction to access the CP15
register.
+-----+-+-------+-------+-------+
|opc_2|0| CRm |0 0 0 0| nbr |
+-----+-+-------+-------+-------+
Normally opc_2 and CRm are zero and therefore you can simply enter the CP15 register number.
In the register definition file "reg720t.def" you will find some examples.
ARM920T:
Via JTAG, CP15 registers are accessed either direct (physical access mode) or via interpreted MCR/
MRC instructions. Read also ARM920T manual, part "Debug Support - Scan Chain 15".
Register number for physical access mode (bit 12 = 0):
+-----+-+-----+-+-----+-+-------+
|0 0 0|0|0 0 0|i|0 0 0|x| nbr |
+-----+-+-----+-+-----+-+-------+
The bit "i" selects the instruction cache (scan chain bit 33), the bit "x" extends access to register 15
(scan chain bit 38).
Register number for interpreted access mode (bit 12 = 1):
+-----+-+-------+-----+-+-------+
|opc_2|1| CRm |opc_1|0| nbr |
+-----+-+-------+-----+-+-------+
The 16bit register number is used to build the appropriate MCR/MRC instruction.
ARM940T, ARM946E, ARM966E:
The CP15 registers are directly accessed via JTAG.
+-----+-+-----+-+-----+-+-------+
|0 0 0|0|0 0 0|i|0 0 0|x| nbr |
+-----+-+-----+-+-----+-+-------+
The bit "i" selects the instruction cache (scan chain bit 32), the bit "x" extends access to register 6
(scan chain bit 37). In the register definition file "reg940t.def" you will find some examples.
