Background Debug Module (S12XBDMV2)
MC9S12XHY-Family Reference Manual Rev. 1.01
Freescale Semiconductor
205
5.3.2.4
BDM Global Page Index Register (BDMGPR)
Figure 5-6. BDM Global Page Register (BDMGPR)
Read: All modes through BDM operation when not secured
Write: All modes through BDM operation when not secured
5.3.3
Family ID Assignment
The family ID is a 8-bit value located in the firmware ROM (at global address: 0x7FFF0F). The read-only
value is a unique family ID which is 0xC1 for S12X devices.
5.4
Functional Description
The BDM receives and executes commands from a host via a single wire serial interface. There are two
types of BDM commands: hardware and firmware commands.
Hardware commands are used to read and write target system memory locations and to enter active
background debug mode, see
Section 5.4.3, “BDM Hardware Commands”
. Target system memory
includes all memory that is accessible by the CPU.
Firmware commands are used to read and write CPU resources and to exit from active background debug
mode, see
Section 5.4.4, “Standard BDM Firmware Commands”
. The CPU resources referred to are the
accumulator (D), X index register (X), Y index register (Y), stack pointer (SP), and program counter (PC).
Hardware commands can be executed at any time and in any mode excluding a few exceptions as
highlighted (see
Section 5.4.3, “BDM Hardware Commands”
) and in secure mode (see
Section 5.4.1,
“Security”
). Firmware commands can only be executed when the system is not secure and is in active
background debug mode (BDM).
Register Global Address 0x7FFF08
7
6
5
4
3
2
1
0
R
BGAE
BGP6
BGP5
BGP4
BGP3
BGP2
BGP1
BGP0
W
Reset
0
0
0
0
0
0
0
0
Table 5-5. BDMGPR Field Descriptions
Field
Description
7
BGAE
BDM Global Page Access Enable Bit — BGAE enables global page access for BDM hardware and firmware
read/write instructions The BDM hardware commands used to access the BDM registers (READ_BD_ and
WRITE_BD_) can not be used for global accesses even if the BGAE bit is set.
0 BDM Global Access disabled
1 BDM Global Access enabled
6–0
BGP[6:0]
BDM Global Page Index Bits 6–0 — These bits define the extended address bits from 22 to 16. For more
detailed information regarding the global page window scheme, please refer to the S12X_MMC Block Guide.
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