MC68HC705B16CFN Freescale Semiconductor, MC68HC705B16CFN Datasheet - Page 176
Manufacturer Part Number
IC MCU 2.1MHZ 15K OTP 52-PLCC
Specifications of MC68HC705B16CFN
Number Of I /o
Program Memory Size
15KB (15K x 8)
Program Memory Type
256 x 8
352 x 8
Voltage - Supply (vcc/vdd)
4.5 V ~ 5.5 V
-40°C ~ 85°C
Package / Case
Lead Free Status / RoHS Status
Contains lead / RoHS non-compliant
A 10-byte stack is also reserved at the top of the RAM allowing, for example, one interrupt and two
Program execution is triggered by sending a negative (bit 7 set) high address; execution starts at
address XADR ($0083).
The RAM addresses between $0050 and $0082 are used by the loader and are therefore not
available to the user during serial loading/executing.
The RAM bootstrap program will start loading the RAM with external data (e.g. from a 2564 or
2764 EPROM). Before loading a new byte, the state of the PD4/AN4 pin is checked; if this pin goes
to level ‘0’, or if the RAM is full, then control is given to the loaded program at address $0050.
If the data is supplied by a parallel interface, handshaking will be provided by PC5 and PC6
disabled by connecting together PC5 and PC6.
programs can be loaded in turn from the EPROM. Selection is accomplished by means of the
switches connected to the EPROM higher address lines (A8 through A10). If the user program sets
PC0 to level ‘1’, the external EPROM will be disabled, rendering both port A outputs and port B
The EPROM parallel bootstrap loader circuit
. The high order address lines will be at zero. The LEDs will stay off.
shows a circuit that can be used to load the RAM with short test programs. Up to 8
RAM parallel bootstrap load and execute
shows a suitable circuit.
C-10. If the data comes from an external EPROM, the handshake can be
Table C-3 Bootstrap vector targets in RAM
Timer output compare
Timer input capture
Vector targets in RAM
C-6) can also be used, provided VPP is tied
shows address and data bus timing.