MC68HC908GR4MP datasheet(137/286 Pages) FREESCALE

137 / 286 page

Functional Description

MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7

Freescale Semiconductor

137

15.3.5 Commands

The monitor ROM firmware uses these commands:

•

READ (read memory)

•

WRITE (write memory)

•

IREAD (indexed read)

•

IWRITE (indexed write)

•

READSP (read stack pointer)

•

RUN (run user program)

The monitor ROM firmware echoes each received byte back to the PTA0 pin for error checking. An 11-bit

delay at the end of each command allows the host to send a break character to cancel the command. A

delay of two bit times occurs before each echo and before READ, IREAD, or READSP data is returned.

The data returned by a read command appears after the echo of the last byte of the command.

NOTE

Wait one bit time after each echo before sending the next byte.

Figure 15-5. Read Transaction

Figure 15-6. Write Transaction

READ

ECHO

FROM

HOST

ADDRESS

HIGH

ADDRESS

HIGH

ADDRESS

LOW

ADDRESS

LOW

DATA

RETURN

13, 2

Notes:

2 = Data return delay, 2 bit times

3 = Cancel command delay, 11 bit times

4 = Wait 1 bit time before sending next byte.

1 = Echo delay, 2 bit times

WRITE

ECHO

FROM

HOST

ADDRESS

HIGH

ADDRESS

HIGH

ADDRESS

LOW

ADDRESS

LOW

DATA

Notes:

2 = Cancel command delay, 11 bit times

3 = Wait 1 bit time before sending next byte.

32, 3

1 = Echo delay, 2 bit times

MC68HC908GR4MP Datasheet(PDF) 137 Page - Freescale Semiconductor, Inc

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