MC68HC05B4 Datasheet, PDF (173/298 Pages) Motorola, Inc – High-density Complementary Metal Oxide Semiconductor (HCMOS) Microcomputer Unit

C.5.1 Erased EPROM verification
The flowchart in Figure C-3 and Figure C-4 shows that the on-chip bootstrap routines can be used
to check if the EPROM is erased (all $00s). If a non $00 byte is detected, the red LED stays on
and the routine will stay in a loop. Only when the whole EPROM content is verified as erased will
the green LED be turned on.
C.5.2 EPROM parallel bootstrap load
When this mode is selected, the EPROM is loaded in increasing address order with non EPROM
segments being skipped by the loader. Simultaneous programming is performed by reading four
bytes of data before actual programming is performed, thus dividing the loading time of the internal
EPROM by four.
When PD2=0, the programming time is set to 5 milliseconds and the program/verify routine takes
approximately 15 seconds.
Parallel data is entered through Port A, while the 13-bit address is output on port B and PC0 to
PC4. If the data comes from an external EPROM, the handshake can be disabled by connecting
together PC5 and PC6. If the data is supplied via a parallel interface, handshaking will be provided
by PC5 and PC6 according to the timing diagram of Figure C-5.
During programming, the green LED flashes at about 3 Hz.
Upon completion of the programming operation, the EPROM content is checked against the
external data source. If programming is verified the green LED stays on, while an error causes the
red LED to be turned on. Figure C-6 shows a circuit that can be used to program the EPROM (or
to load and execute data in the RAM).
Note:
The entire EPROM can be loaded from the external source; if it is desired to leave a
segment undisturbed, the data for this segment should be all zeros.
Address
HDSK out
(PC5)
DATA
HDSK in
(PC6)
F29
MC68HC05B6
Rev. 4
Data read
Figure C-5 Timing diagram with handshake
MC68HC705B5
Data read
14
TPG
MOTOROLA
C-11