MC68181 Datasheet, PDF (62/119 Pages) Freescale Semiconductor, Inc – Advance Information ROAMING FLEX chip SIGNAL PROCESSOR

MC68181
Freescale Semiconductor, Inc.
Packet Communication Initiated by the FLEX chip IC
SS
2
4
READY 1
SCK
3
MOSI
D31
D1 D0
D31
D1 D0
D31
D1 D0
MISO
D31
D1 D0
D31
D1 D0
D31
D1 D0
High Impedance State
Figure B-1 Typical Multiple Packet Communications Initiated by the Host
AA1230
When the host sends a packet, it will also receive a valid packet from the FLEX chip
IC. If the FLEX chip IC is enabled (See Checksum Packet on page B-6.) and has no
other packets waiting to be sent, the FLEX chip IC will send a status packet. The host
must transition the SS pin from high to low to begin each 32-bit packet. The FLEX
chip IC must see a negative transition on the SS pin in order for the host to initiate
each packet communication.
PACKET COMMUNICATION INITIATED BY THE FLEX CHIP IC
When the FLEX chip IC has a packet for the host to read, the following occurs (see
Figure B-2):
1. The FLEX chip IC drives the READY pin low.
2. If the FLEX chip IC is not already selected, the host selects the FLEX chip IC
by driving the SS pin low.
3. The host receives (and sends) a 32-bit packet.
4. The host de-selects the FLEX chip IC by driving the SS pin high (optional).
B-2
MC68181 Technical Data Sheet
MOTOROLA
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