MC68HC705B16CFN Freescale Semiconductor, MC68HC705B16CFN Datasheet - Page 175
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
The serial routine communicates through the SCI with an external host, typically a PC, by means
of an RS232 link at 9600 baud, 8-bit, no parity and full duplex.
Data format is not ASCII, but 8-bit binary, so a complementary program must be run by the host
to supply the required format. Such a program is available for the IBM PC from Freescale.
The EPROM bootstrap routines are used to customise the OTP EPROM. To increase the speed
of programming, four bytes are programmed in parallel while the data is simultaneously
transmitted and received in full duplex. This implies that while 4 bytes are being programmed, the
next 4 bytes are received and the preceding 4 bytes are echoed. The format accepted by the serial
loader is as follows:
Address n must have the two LSBs at zero so that n, n+1, n+2 and n+3 have identical MSBs.
These blocks of four bytes do not need to be contiguous, as a new address is transmitted for each
The protocol is as follows:
After reset, the MC68HC705B5 serial bootstrap routine will first echo two blocks of four bytes at
$0000, as no data is programmed yet.
If the data sent in is $00, no programming in the EPROM takes place, and the contents of the
accessed location are returned as a prompt. The entire EPROM memory can be read in this
fashion (serial dump). The red LED will be on if the data read from the EPROM is not $00.
Serial RAM loading and execute can be accomplished in this mode. A RAM byte will be written if
the address sent by the host in the serial protocol points to the RAM.
In the RAM bootloader mode, all interrupt vectors are mapped to pseudo-vectors in RAM (see
pseudo-vector is allowed three bytes of space rather than the two bytes for normal vectors,
because an explicit jump (JMP) opcode is needed to cause the desired jump to the user’s
C-3). This allows programmers to use their own service-routine addresses. Each
1 The MC68HC705B5 sends the last two bytes programmed to the host as a
1) In response to the first byte prompt, the host sends the first address byte.
2) After receiving the first address byte, the MC68HC705B5 sends the next
3) The exchange of data continues until the MC68HC705B5 has sent the four
4) If the data is non zero, it is programmed at the address provided, while the
5) Loop to 1.
[address n high] [address n low] [data(n)] [data (n+1)] [data (n+2)] [data (n+3)]
prompt; this allows verification by the host of proper programming.
data bytes and the host has sent the 2 address data bytes and 4 data bytes.
next address and bytes are received and the previous data is echoed.
EPROM (RAM) serial bootstrap load and execute