Signal Description
MOTOROLA
MC68302 USER’S MANUAL
5-13
**
If DTACK is generated automatically (internally) by the chip-select logic, then it is an output. Otherwise, it is an
input.
***
BERR is an open-drain output, and may be asserted by the IMP when the hardware watchdog is used or when
the chip-select logic detects address conflict or write protect violation. BERR may be asserted by external logic in
all cases.
# Applies to disable CPU mode only. The internal signal IBCLR is used otherwise.
## Applies to disable CPU mode only, otherwise N/A.
5.11 PHYSICAL LAYER SERIAL INTERFACE PINS
The physical layer serial interface has 24 pins, and all but one of them have multiple func-
tionality. The pins can be used in a variety of configurations in ISDN or non-ISDN environ-
ments. Table 5-3 shows the functionality of each group of pins and their internal connection
to the three SCC and one SCP controllers. The physical layer serial interface can be config-
ured for non-multiplexed operation (NMSI) or multiplexed operation that includes IDL, GCI,
and PCM highway modes. IDL and GCI are ISDN interfaces. When working in one of the
multiplexed modes, the NMSI1/ISDN physical interface can be connected to all three SCC
controllers.
NOTE: Each one of the parallel I/O pins can be configured individually.
Table 5-3. Bus Signal Summary—IDMA and SDMA
IDMA Master
Access To
SDMA Master
Access To
Signal Name
Pin Type
Internal
Memory
Space
External
Memory
Space
Internal
Memory
Space
External
Memory
Space
A23–A1, FC–FC0,
AS, UDS, LDS, R/W, RMC
BCLR
IAC
D15—D0 Read
D15—D0 Write
I/O
O
O
N/A
O
I/O Open Drain
O
I/O
I/O
I #
O
O
O
I #
O
I
O
**
N/A
N/A
N/A
N/A
O
O
I
O
**
DTACK
I/O
O
N/A
BR
BG
BGACK
HALT
RESET
I/O
I/O
I/O
O ##
I ##
O
I
I
***
O ##
I ##
O
I
I
***
N/A
N/A
N/A
N/A
N/A
O ##
I ##
O
I
I
***
I/O Open Drain
I/O Open Drain
BERR
I/O Open Drain
I/O
I/O
N/A
I/O
Table 5-4. Serial Interface Pin Functions
First Function
Connected To
Second Function
Connected To
NMSI1 (8)
NMSI2 (8)
NMSI3 (5)
NMSI3 (3)
SCC1 Controller
SCC2 Controller
SCC3 Controller
SCC3 Controller
ISDN Interface
PIO—Port A
PIO—Port A
SCP
SCC1/SCC2/SCC3
Parallel I/O
Parallel I/O
SCP Controller