Motorola MC68824 User Manual page 100

The mechanisms by which the TBC obtains acknowledgements from the physical layer are de-
scribed in 3.8 MODEM CONTROL. If the TBC receives a physical layer error encoding while in the
MAC mode, it will put itself in the offline mode and set the modem error bit in interrupt status
word 1 (see 2.2.11 Interrupt Status Words).
5.7 SIGNAL SUMMARY
Table 5-2 is a summary of all signals discussed in the previous paragraphs.
Table 5-2. Signal Summary
Signal Name
Menemonic Input/Output Active State Driver Type
Address Bus A1-A2
Input/Output Three State
Address Bus
A3-A31 Output Three State
Data Bus
DO-D15 Input/Output Three State
Function Codes FCO-FC3
Output Three State
Bus Exception Codes BECO-BEC2
Input Low
Upper Data Strobe
UDS/AO Input/Output
Low/High
Three State
1
Lower Data Strobe
LDS/DS Input/Output Low/Low Three State
1
Address Strobe AS Input/Output Low Three State
1
ReadtWrite
RiW Input/Output
High/Low
Three State
1
Chip Select
CS Input Low
Data Transfer Acknowledge
DTACK Input/Output Low Three State
1
Bus Request BR Output Low Open Drain
2
Bus Grant
BG Input Low
Bus Grant Acknowledge
BGACK Input/Output Low Three State
1
Receive Clock
RXCLK Input
Indication Channel
SMIND Input Low
Indication Channel RXSYMO Input
Indication Channel RXSYM1 Input
Indication Channel RXSYM2 Input
Transmit Clock TXCLK Input
Request Channel SMREQ Input Low
Request Channel TXSYMO Output
Request Channel TXSYM1 Output
Request Channel TXSYM2 Output
Interrupt Request IRQ Output Low Open Drain
2
Interrupt Acknowledge
lACK Input Low
Clock CLK Input
NOTES:
1. These signals require a pullup resistor to maintain a high voltage when in the high-impedance
or negated state. However, when these signals go to the high-impedance or negated state they
will first drive the pin high momentarily to reduce the signal rise time.
2. These signals are wire-ORed and require a pullup resistor to maintain a high voltage when not
driven.
MC68824 USER'S MANUAL MOTOROLA
5-9
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