M68HC12A4EVB Freescale Semiconductor, M68HC12A4EVB Datasheet - Page 281

• Manufacturer Part Number: M68HC12A4EVB
• Manufacturer: Freescale Semiconductor

Specifications of M68HC12A4EVB

• Lead Free Status / Rohs Status: Not Compliant

FRZ1 and FRZ0 — Background Debug (Freeze) Enable Bits
17.3.5 ATD Control Register 4
The ATD control register 4 (ATDCTL4) selects the clock source and sets up the prescaler. Writes to the
ATD control registers initiate a new conversion sequence. If a write occurs while a conversion is in
progress, the conversion is aborted and ATD activity halts until a write to ATDCTL5 occurs.
S10BM — ATD 10-Bit Mode Control Bit
SMP1 and SMP0 — Select Sample Time Bits
PRS4–PRS0 — Select Divide-By Factor for ATD P-Clock Prescaler Bits
Freescale Semiconductor
When debugging an application, it is useful in many cases to have the ATD pause when a breakpoint
is encountered. These two bits determine how the ATD will respond when background debug mode
becomes active. See
These bits are used to select one of four sample times after the buffered sample and transfer has
occurred. See
The binary value written to these bits (1 to 31) selects the divide-by factor for the modulo counter-based
prescaler. The P clock is divided by this value plus one, and then fed into a divide-by-two circuit to
generate the ATD module clock. The divide-by-two circuit ensures symmetry of the output clock signal.
0 = 8-bit operation
1 = 10-bit operation
SMP1
Address: $0064
Reset:
Read:
0
0
1
1
Write:
FRZ1
Table
0
0
1
1
SMP0
Table 17-1. ATD Response to Background Debug Enable
S10BM
0
1
0
1
Bit 7
17-2.
Table
0
FRZ0
Figure 17-6. ATD Control Register 4 (ATDCTL4)
0
1
0
1
16 ATD clock periods
2 ATD clock periods
4 ATD clock periods
8 ATD clock periods
Table 17-2. Final Sample Time Selection
17-1.
SMP1
Sample Time
6
0
Continue conversions in active background mode
Reserved
Finish current conversion, then freeze
Freeze when BDM is active
M68HC12B Family Data Sheet, Rev. 9.1
Final
SMP0
5
0
PRS4
18 ATD clock periods
20 ATD clock periods
24 ATD clock periods
32 ATD clock periods
4
0
Conversion Time
ATD Response
Total 8-Bit
PRS3
3
0
PRS2
2
0
20 ATD clock periods
22 ATD clock periods
26 ATD clock periods
34 ATD clock periods
Conversion Time
Total 10-Bit
PRS1
1
0
PRS0
Bit 0
1
ATD Registers
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