Page 5
PRELIMINARY
C8051F020/1/2/3
16.1.Accessing XRAM..........................................................................................................143
16.1.1. 16-Bit MOVX Example.......................................................................................143
16.1.2. 8-Bit MOVX Example.........................................................................................143
16.2.Configuring the External Memory Interface.................................................................144
16.3.Port Selection and Configuration..................................................................................144
16.4.Multiplexed and Non-multiplexed Selection.................................................................146
16.4.1. Multiplexed Configuration ..................................................................................146
16.4.2. Non-multiplexed Configuration...........................................................................147
16.5.Memory Mode Selection...............................................................................................148
16.5.1. Internal XRAM Only...........................................................................................148
16.5.2. Split Mode without Bank Select..........................................................................148
16.5.3. Split Mode with Bank Select...............................................................................149
16.5.4. External Only.......................................................................................................149
16.6.Timing
.......................................................................................................................150
16.6.1. Non-multiplexed Mode........................................................................................151
16.6.1.1.16-bit MOVX: EMI0CF[4:2] = ‘101’, ‘110’, or ‘111’................................151
16.6.1.2.8-bit MOVX without Bank Select: EMI0CF[4:2] = ‘101’ or ‘111’............152
16.6.1.3.8-bit MOVX with Bank Select: EMI0CF[4:2] = ‘110’...............................153
16.6.2. Multiplexed Mode................................................................................................154
16.6.2.1.16-bit MOVX: EMI0CF[4:2] = ‘001’, ‘010’, or ‘011’................................154
16.6.2.2.8-bit MOVX without Bank Select: EMI0CF[4:2] = ‘001’ or ‘011’............155
16.6.2.3.8-bit MOVX with Bank Select: EMI0CF[4:2] = ‘010’...............................156
17. PORT INPUT/OUTPUT.....................................................................................................159
17.1.Ports 0 through 3 and the Priority Crossbar Decoder....................................................161
17.1.1. Crossbar Pin Assignment and Allocation............................................................161
17.1.2. Configuring the Output Modes of the Port Pins..................................................162
17.1.3. Configuring Port Pins as Digital Inputs...............................................................163
17.1.4. External Interrupts (IE6 and IE7) ........................................................................163
17.1.5. Weak Pull-ups......................................................................................................163
17.1.6. Configuring Port 1 Pins as Analog Inputs (AIN1.[7:0])......................................163
17.1.7. External Memory Interface Pin Assignments......................................................164
17.1.8. Crossbar Pin Assignment Example......................................................................166
17.2.Ports 4 through 7 (C8051F020/2 only)..........................................................................175
17.2.1. Configuring Ports which are not Pinned Out.......................................................175
17.2.2. Configuring the Output Modes of the Port Pins..................................................175
17.2.3. Configuring Port Pins as Digital Inputs...............................................................176
17.2.4. Weak Pull-ups......................................................................................................176
17.2.5. External Memory Interface..................................................................................176
18. SYSTEM MANAGEMENT BUS / I2C BUS (SMBUS0).................................................181
18.1.Supporting Documents..................................................................................................182
18.2.SMBus Protocol.............................................................................................................183
18.2.1. Arbitration............................................................................................................183
18.2.2. Clock Low Extension...........................................................................................183
18.2.3. SCL Low Timeout...............................................................................................184
18.2.4. SCL High (SMBus Free) Timeout.......................................................................184