Information

MCP2120/22 Developer’s Board User’s Guide

TABLE 2-3: MCP212XDM FIRMWARE PROGRAM SELECTION

2.2.1.1 FIRMWARE OPERATION - Generate Clock only (determined by

RD0:RD2)

The PIC firmware reads the state of the RD7 and RD3 signals. If the signals indicate

that the device is the MCP2120 and to use the PIC as the clock source, then the PIC

will source a frequency that is determined by the RD2:0 signals.

The PIC firmware reads the state of the RD3 signal to determine if the encoder/decoder

device is an MCP2120 or MCP2122.

If the device is the MCP2120, then the PWM output frequency is set to 3.6864 MHz and

the PIC drives the MCP2120’s BAUD2:0 signals with the selected baud rate from the

state of the RD2:0 signals.

If the device is the MCP2122, then the PWM output frequency is determined from the

state of the RD2:0 signals.

This mode requires that the MCP2122’s TX and RX signals are directly connected to

the MAX3238 compatible device.

2.2.1.2 FIRMWARE OPERATION - Generate Clock only (@ 3.6864 MHz)

The PIC firmware reads the state of the RD7 and RD3 signals. If the signals indicate

that the device is the MCP2120 and to use the PIC as the clock source, then the PIC

will source a 3.6864 MHz clock to be used by the MCP2120 device. The PIC will drive

the MCP2120’s BAUD2:0 signals with the selected baud rate from the state of the

RD2:0 signals.

Although the clock could drive the MCP2122’s 16XCLK pin, the frequency is higher

than the maximum specification.

This mode requires that the MCP2120’s TX and RX signals are directly connected to

the MAX3238 compatible device.

MODE

Program Comment

73 6:4

1 1 1

Generate Clock only (determined by RD0:RD2) MCP2122 uses PIC 16XCLK

0 No Clock Generation MCP2120 uses Crystal

1 Generate Clock only (determined by RD0:RD2) MCP2122 uses PIC 16XCLK

0 Generate Clock only (@ 3.6864 MHz) MCP212x uses PIC Clock

1 1 0 Pass Data Through (UART1 <---> UART2)

1 0 1 Pass Data Through (UART1 --> UART2) with UART2

fixed at 115,200 Baud

1 0 0 Echo Data Received and change case (A --> a, a --> A)

0 1 1 Stream a Data Table See Appendix E.

0 1 0 RESERVED

0 0 1 RESERVED

0 0 0 RESERVED

Legend:X = Undefined (either "1" or "0").