Mc68824 Signals - Motorola MC68824 User Manual

II
SYSTEM INTERFACE
ADDRESS BUS {
DATABUS {
FUNCTION CODES {
BUS
CONTROL
BUS {
ARBITRATION .
INTERRUPT {
CONTROL
BUS EXCEPTION {
CONDITIONS
-
A
<
Al
A2
~
A3-A31
I\.
00-015
"' -
V
FCO
FCI
FC2
FC3
DTACK
R/W
UDS/AO
LOS/OS
AS
CS
Bli
BG
BGACK
IRQ
lACK
BE CO
BECI
BEC2
VOD
CLK
GND
MC68824
SMREQ
TXClK
TXSYM2
TXSYMI
TXSYMO
SMIND
""'- RXClK
RXSYM2
RXSYMI
RXSYMO
SERIAL INTERFACE
}
PHYSICAL
DATA
REQUEST
CHANNEL
}
PHYSICAL
DATA
INDICATION
CHANNEL
Figure 5-1. MC68824 Signals
these encodings as desired. The user is not required to
implement function codes. If the function code pins are
not connected, the user can ignore SET FUNCTION CODE
commands (see 3.5.3 Set Value).
5.3.2 Bus Exception Conditions (BECO-BEC2)
These input lines provide an encoded signal that indi-
cates an abnormal bus condition such as a bus error or
reset. The three-bit bus exception control codes allow
for eight different bus termination conditions. BECD is
the least significant bit and BEC2 is the most significant
bit. Table 5-1 shows the eight conditions.
MOTOROLA
5-2
Table 5-1. Bus Exception Conditions
BEC2 BEC1 BECD Condition
H
H
H
No Exception
H
H
L
Halt (Release Bus)
H
L
H Bus Error
H
L L Retry
L
H
H Relinquish and Retry
L H L Undefined (Reserved)
L
L
H
Undefined (Reserved)
L L L Reset
MC68824 USER'S MANUAL