MC68HC711E20CFS2 MOTOROLA [Motorola, Inc], MC68HC711E20CFS2 Datasheet - Page 222

• Manufacturer Part Number: MC68HC711E20CFS2
• Description: Microcontrollers
• Manufacturer: MOTOROLA [Motorola, Inc]

Freescale Semiconductor, Inc.
Application Note
To understand the detailed operation of the EPROM programming utility,
refer to
Figure 4
during the following discussion.
Figure 4
is composed
of three interrelated parts. The upper-left portion shows the flowchart of
the PROGRAM utility running in the boot ROM of the MCU. The upper-
right portion shows the flowchart for the user-supplied driver program
running in the host computer. The lower portion of
Figure 4
is a timing
sequence showing the relationship of operations between the MCU and
the host computer. Reference numbers in the flowcharts in the upper
half of
Figure 4
have matching numbers in the lower half to help the
reader relate the three parts of the figure.
The shaded area [1] refers to the software and hardware latency in the
MCU leading to the transmission of a character (in this case, the $FF).
The shaded area [2] refers to a similar latency in the host computer (in
this case, leading to the transmission of the first data character to the
MCU).
The overall operation begins when the MCU sends the first character
($FF) to the host computer, indicating that it is ready for the first data
character. The host computer sends the first data byte [3] and enters its
main loop. The second data character is sent [4], and the host then waits
[5] for the first verify byte to come back from the MCU.
After the MCU sends $FF [8], it enters the WAIT1 loop [9] and waits for
the first data character from the host. When this character is received
[10], the MCU programs it into the address pointed to by the Y index
register. When the programming time delay is over, the MCU reads the
programmed data, transmits it to the host for verification [11], and
returns to the top of the WAIT1 loop to wait for the next data character
[12]. Because the host previously sent the second data character, it is
already waiting in the SCI receiver of the MCU. Steps [13], [14], and [15]
correspond to the second pass through the WAIT1 loop.
Back in the host, the first verify character is received, and the third data
character is sent [6]. The host then waits for the second verify character
[7] to come back from the MCU. The sequence continues as long as the
host continues to send data to the MCU. Since the WAIT1 loop in the
PROGRAM utility is an indefinite loop, reset is used to end the process
in the MCU after the host has finished sending data to be programmed.
AN1060 — Rev. 1.0
222
MOTOROLA
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