Motorola MC68328 Technical Information PDF herunterladen (Seite 23)

Software Development

FLEX System Software

FLEX Alphanumeric Chip MC68175 Interface

3-5

Upon reset or at power-up, the entire FLEX Alphanumeric Chip IC is “disabled” from

sending any information except the

part ID.

The FLEX Alphanumeric Chip will

continue to assert interrupt and broadcast the

part ID

until the host processor, via the

interrupt service routine, recognizes the FLEX IC by sending back to the FLEX

Alphanumeric Chip the proper

Checksum

packet. The

Checksum

packet can be

considered as the required handshaking signal from the host to recognize and “enable”

the FLEX IC. The algorithm for calculating the

Checksum

value is embedded in the FLEX

One-Way Stack software. Ordinarily, this initialization procedure requires two SPI data

transfers, as described in

Figure 3-2

FLEX Alphanumeric Chip Enabling Steps

After the FLEX Alphanumeric Chip receives the correct

Checksum

packet from the FLEX

One-Way Stack software, the chip is “enabled”. It stops asserting interrupts to the host

processor until it has new information to send to the host, such as a new page. The FLEX

Alphanumeric Chip is “disabled” only in the sense that the host MPU cannot read data

from the FLEX Alphanumeric Chip IC.

SPI Communication

FLEX

Host

SPI Communication

Host

Packet = <32-bit ID>

Packet = 00000000

Packet = <32-bit ID>

Packet = <32-bit Checksum>

First SPI Data

Transfer:

Second SPI Data

Transfer:

Chip is

Disabled

Chip is

Enabled

AA1422

Alphanumeric

Chip

FLEX

Alphanumeric

Chip

Frees

cale Semiconductor,

Freescale Semiconductor, Inc.

For More Information On This Product,

Go to: www.freescale.com

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