General Information
Performance Notes
M68HC12A4EVB Evaluation Board — Rev. 1
User’s Manual
MOTOROLA
General Information
19
Figure 1-2. System Block Diagram
1.4 Performance Notes
The M68HC12A4EVB’s external RAM memory chips, U4 and U6A, were
chosen to emphasize the EVB’s low-voltage and low-power operational
capability over the range of +3.5 to +5.0 Vdc.
However, these parts are not fast enough to operate at the 16-MHz speed of the
factory-supplied clock oscillator. To use them at this external clock speed, the
D-Bug12 startup code programs the MCU’s RAM chip select to insert one wait
state into each access of external RAM. Thus, when programs are run from
PROTO-
TYPE
AREA
J8 / J9
S1 RESET
MCU
MC68HC812A4
M68HC12A4EVB
SCI0
SCI1
ON-CHIP
EEPROM
RAM
ON-CHIP
112 PINS
TOTAL
RS-232C
TRANSCEIVER
J3
J2
J6
J5
TERMINAL
SPARE
POWER
BDM INTERFACE
S2 – PROGRAM ABORT
CLOCK
EXTERNAL
ROM
AND
RAM
GLUE
LOGIC
EXTAL
XTAL
XFC
V
DD
/6
V
SS
/6
PA [7:0]
PB [7:0]
PC [7:0]
PD [7:0]
PE [7:0]
PF [6:0]
PG [5:0]
PH [7:0]
PJ [7:0]
PAD [7:0]
V
RH
, V
RL
BKGD
PS [7:0]
PT [7:0]
RESET
J7
BKGD
EXTAL
PE0/XIRQ
PA [7:0]
PB [7:0]
PC [7:0]
PD [7:0]
PE [6:0]
PG [5:0]
PE2/RW
PE3/LSTRB
EXTERNAL CLOCK
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Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
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