AUTOMOTIVE 80C51FA/83C51FA
PIN DESCRIPTIONS
VCC: Supply voltage.
VSS: Circuit ground.
Port 0: Port 0 is an 8-bit, open drain, bidirectional I/O port. As an output port each pin can sink several LS TTL inputs. Port 0 pins that have 1's written to them float, and in that state can be used as high-im- pedance inputs.
Port 0 is also the multiplexed low-order address and data bus during accesses to external Program and Data Memory. In this application it uses strong inter- nal pullups when emitting1's, and can source and sink several LS TTL inputs.
Port 0 outputs the code bytes during program verifi- cation. External pullup resistors are required during program verification.
Port 1: Port 1 is an 8-bit bidirectional I/O port with internal pullups. The Port 1 output buffers can drive LS TTL inputs. Port 1 pins that have 1's written to them are pulled high by the internal pullups, and in that state can be used as inputs. As inputs, Port 1 pins that are externally pulled low will source current (IIL, on the datasheet) because of the internal pull- ups.
In addition, Port 1 serves the functions of the follow- ing special features of the 83C51FA:
Port Pin | Alternate Function |
P1.0 | T2 (External Count Input to Timer/ |
| Counter 2) |
P1.1 | T2EX (Timer/Counter 2 Capture/ |
| Reload Trigger and Direction Control) |
P1.2 | ECI (External Count Input to the PCA) |
P1.3 | CEX0 (External I/O for Compare/ |
| Capture Module 0) |
P1.4 | CEX1 (External I/O for Compare/ |
| Capture Module 1) |
P1.5 | CEX2 (External I/O for Compare/ |
| Capture Module 2) |
P1.6 | CEX3 (External I/O for Compare/ |
| Capture Module 3) |
P1.7 | CEX4 (External I/O for Compare/ |
| Capture Module 4) |
Port 2: Port 2 is an 8-bit bidirectional I/O port with internal pullups. The Port 2 output buffers can drive LS TTL inputs. Port 2 pins that have 1's written to them are pulled high by the internal pullups, and in that state can be used as inputs. As inputs, Port 2 pins that are externally pulled low will source current (IIL, on the datasheet) because of the internal pull- ups.
Port 2 emits the high-order address byte during fetches from external Program Memory and during accesses to external Data Memory that use 16-bit addresses (MOVX @DPTR). In this application it uses strong internal pullups when emitting 1's. Dur- ing accesses to external Data Memory that use 8-bit
