MC68HC912BL16 Datasheet, PDF (122/128 Pages) Freescale Semiconductor, Inc – 16-Bit Microcontroller

Freescale Semiconductor, Inc.
SHIFTER — BDM Shift Register
Bit 15
14
13
12
11
10
S15
S14
S13
S12
S11
S10
(BDM) $FF02, $FF03
9
Bit 8
S9
S8
Bit 7
6
5
4
3
2
1
Bit 0
S7
S6
S5
S4
S3
S2
S1
S0
The 16-bit SHIFTER register contains data being received or transmitted via the serial interface. It is
also used by the BDM firmware for temporary storage. The register can be read or written in all modes
but is not normally accessed by users.
ADDRESS — BDM Address Register
Bit 15
14
13
12
11
10
A15
A14
A13
A12
A11
A10
(BDM) $FF04, $FF05
9
Bit 8
A9
A8
Bit 7
6
5
4
3
2
1
Bit 0
A7
A6
A5
A4
A3
A2
A1
A0
The 16-bit ADDRESS register is temporary storage for BDM hardware and firmware commands. The
register can be read in all modes but is not normally accessed by users. It is written only by BDM hard-
ware.
CCRSAV — BDM CCR Holding Register
Bit 7
6
5
CCR7 CCR6 CCR5
4
CCR4
3
CCR3
2
CCR2
1
CCR1
(BDM) $FF06
Bit 0
CCR0
The CCRSAV register is used to save the CCR of the users program when entering BDM. It is also used
for temporary storage in the BDM firmware. The register is initialized by the firmware to equal the CPU
CCR register.
15.3 Breakpoints
Hardware breakpoints are used to debug software on the MC68HC912BL16 by comparing actual ad-
dress and data values to predetermined data in setup registers. A successful comparison will place the
CPU in background debug mode (BDM) or initiate a software interrupt (SWI). Breakpoint features de-
signed into the MC68HC912B32 include:
• Mode selection for BDM or SWI generation
• Program fetch tagging for cycle of execution breakpoint
• Second address compare in dual address modes
• Range compare by disable of low byte address
• Data compare in full feature mode for non-tagged breakpoint
• Byte masking for high/low byte data compares
• R/W compare for non-tagged compares
• Tag inhibit on BDM TRACE
15.3.1 Breakpoint Modes
Three modes of operation determine the type of breakpoint in effect.
• Dual address-only breakpoints, each of which will cause a software interrupt (SWI)
MC68HC912BL16
122
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