
C8051F020/1/2/3
Rev. 1.4
5
16.1.Accessing XRAM..........................................................................................................145
16.1.1. 16-Bit MOVX Example.......................................................................................145
16.1.2. 8-Bit MOVX Example.........................................................................................145
16.2.Configuring the External Memory Interface.................................................................146
16.3.Port Selection and Configuration..................................................................................146
16.4.Multiplexed and Non-multiplexed Selection.................................................................148
16.4.1. Multiplexed Configuration ..................................................................................148
16.4.2. Non-multiplexed Configuration...........................................................................149
16.5.Memory Mode Selection...............................................................................................150
16.5.1. Internal XRAM Only...........................................................................................150
16.5.2. Split Mode without Bank Select..........................................................................150
16.5.3. Split Mode with Bank Select...............................................................................151
16.5.4. External Only.......................................................................................................151
16.6.Timing
.......................................................................................................................151
16.6.1. Non-multiplexed Mode........................................................................................153
16.6.1.1.16-bit MOVX: EMI0CF[4:2] = ‘101’, ‘110’, or ‘111’................................153
16.6.1.2.8-bit MOVX without Bank Select: EMI0CF[4:2] = ‘101’ or ‘111’............154
16.6.1.3.8-bit MOVX with Bank Select: EMI0CF[4:2] = ‘110’...............................155
16.6.2. Multiplexed Mode................................................................................................156
16.6.2.1.16-bit MOVX: EMI0CF[4:2] = ‘001’, ‘010’, or ‘011’................................156
16.6.2.2.8-bit MOVX without Bank Select: EMI0CF[4:2] = ‘001’ or ‘011’............157
16.6.2.3.8-bit MOVX with Bank Select: EMI0CF[4:2] = ‘010’...............................158
17. PORT INPUT/OUTPUT.....................................................................................................161
17.1.Ports 0 through 3 and the Priority Crossbar Decoder....................................................163
17.1.1. Crossbar Pin Assignment and Allocation............................................................163
17.1.2. Configuring the Output Modes of the Port Pins..................................................164
17.1.3. Configuring Port Pins as Digital Inputs...............................................................165
17.1.4. External Interrupts (IE6 and IE7) ........................................................................165
17.1.5. Weak Pull-ups......................................................................................................165
17.1.6. Configuring Port 1 Pins as Analog Inputs (AIN1.[7:0])......................................165
17.1.7. External Memory Interface Pin Assignments......................................................166
17.1.8. Crossbar Pin Assignment Example......................................................................168
17.2.Ports 4 through 7 (C8051F020/2 only)..........................................................................177
17.2.1. Configuring Ports which are not Pinned Out.......................................................177
17.2.2. Configuring the Output Modes of the Port Pins..................................................177
17.2.3. Configuring Port Pins as Digital Inputs...............................................................178
17.2.4. Weak Pull-ups......................................................................................................178
17.2.5. External Memory Interface..................................................................................178
18. SYSTEM MANAGEMENT BUS / I2C BUS (SMBUS0).................................................183
18.1.Supporting Documents..................................................................................................184
18.2.SMBus Protocol.............................................................................................................185
18.2.1. Arbitration............................................................................................................185
18.2.2. Clock Low Extension...........................................................................................185
18.2.3. SCL Low Timeout...............................................................................................186
18.2.4. SCL High (SMBus Free) Timeout.......................................................................186