MOTOROLA
MC68306 USER'S MANUAL
2- 5
Table 2-6. Serial Module Signal Summary
Signal Name
Mnemonic
Input/
Output
Three-State During
Bus Arbitration
Pullup Required
Channel A Receiver Serial Data
RxDA
Input
—
Channel A Transmitter Serial
Data
TxDA
Output
No
Channel B Receiver Serial Data
RxDB
Input
—
Channel B Transmitter Serial
Data
TxDB
Output
No
Channel A Clear-to-Send
CTSA
/IP0
Input
—
(1)
Channel A Request-to-Send
RTSA
/OP0
Output
No
Channel B Clear-to-Send
CTSB
/IP1
Input
—
(1)
Channel B Request-to-Send
RTSB
/OP1
Output
No
Crystal Output
X2
Output
No
Crystal Input or External Clock
X1/CLK
Input
—
Parallel Input 2
IP2
Input
—
(1)
Parallel Output 3
OP3
Output
No
NOTES:
1. Pullup may be required, value depends on individual application. Must not be left floating.
Table 2-7. JTAG Signal Summary
Signal Name
Mnemonic
Input/
Output
Three-State During
Bus Arbitration
Pulldown Required
Test Clock
TCK
Input
—
Test Data Input
TDI
Input
—
Test Data Output
TDO
Output
—
Test Mode Select
TMS
Input
—
Test Reset
TRST
Input
—
4.7 K (3)
NOTES:
3. Pin has internal pullup, but external pulldown may be required for correct initialization.
2.1 BUS SIGNALS
The following signals are used for the MC68306 bus.
2.1.1 Address Bus (A23–A1)
This 23-bit, unidirectional, three-state bus is capable of addressing 16 Mbytes of data.
This bus provides the address for bus operation during all cycles except interrupt
acknowledge cycles. During interrupt acknowledge cycles, address lines A1, A2, and A3
provide the level number of the interrupt being acknowledged, and address lines A23–A4