4.3.22. c9, BTCM Region Register

The BTCM Region Register characteristics are:

  • Holds the base address and size of the BTCM.

  • Determines if the BTCM is enabled.

Usage constraints

The BTCM Region Register is:

  • a read/write register

  • accessible in Privileged mode only.


Available in all processor configurations.


Figure 4.40 shows the BTCM Region Register bit assignments.

Figure 4.40. BTCM Region Register bit assignments

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Table 4.41 shows the BTCM Region Register bit assignments.

Table 4.41. BTCM Region Register bit assignments






Base address

Base address. Defines the base address of the BTCM. The base address must be aligned to the size of the BTCM. Any bits in the range [(log2(RAMSize)-1):12] are ignored.

At reset, if LOCZRAMA is set to:

0 =The initial base address is 0x0.

1 =The initial base address is implementation-defined. See Configurable options.

[11:7]-UNP on reads, SBZ on writes.
[6:2]SizeSize. Indicates the size of the BTCM on reads. On writes this field is ignored. See About the TCMs:

b00000 = 0KB

b00011 = 4KB

b00100 = 8KB

b00101 = 16KB

b00110 = 32KB

b00111 = 64KB

b01000 = 128KB

b01001 = 256KB

b01010 = 512kB

b01011 = 1MB

b01100 = 2MB

b01101 = 4MB

b01110 = 8MB




Enables or disables the BTCM:

0 = Disabled

1 = Enabled. The reset value of this field is determined by the INITRAMB input pin.

To access the BTCM Region Register, read or write CP15 with:

MRC p15, 0, <Rd>, c9, c1, 0  ; Read BTCM Region Register
MCR p15, 0, <Rd>, c9, c1, 0  ; Write BTCM Region Register
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