32581C

SuperI/O Module

5.7.3Acknowledge (ACK) Cycle

The ACK cycle consists of two signals: the ACK clock pulse sent by the master with each byte transferred, and the ACK signal sent by the receiving device (see Figure 5-15).

The master generates the ACK clock pulse on the ninth clock pulse of the byte transfer. The transmitter releases

ABD

MSB

the ABD line (permits it to go high) to allow the receiver to send the ACK signal. The receiver must pull down the ABD line during the ACK clock pulse, signalling that it has cor- rectly received the last data byte and is ready to receive the next byte. Figure 5-16illustrates the ACK cycle.

Acknowledge

Signal From Receiver

ABC

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1

 

2 3 - 6

7

 

8

 

 

9

 

 

S

 

 

 

 

 

 

 

 

 

 

 

 

ACK

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Start

Condition

Byte Complete

Interrupt Within

Receiver

1

 

2

 

3 - 8

 

9

 

P

 

 

 

 

 

ACK

 

 

 

 

 

 

Stop Condition

Clock Line Held Low by Receiver While Interrupt is Serviced

Figure 5-15. ACCESS.bus Data Transaction

Data Output

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Transmitter Stays Off Bus

by Transmitter

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

During Acknowledge Clock

Data Output

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Acknowledge

by Receiver

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Signal From Receiver

ABC

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

3 - 6

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

S

1

2

7

 

8

 

 

 

9

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Start

Condition

Figure 5-16. ACCESS.bus Acknowledge Cycle

120

AMD Geode™ SC3200 Processor Data Book

Page 120
Image 120
AMD SC3200 manual Acknowledge ACK Cycle, Abd Msb, Abc Ack