CM312 datasheet(28/56 Pages) ETC

28 / 56 page

CM312 Quad Serial utilityModule

RTD Embedded Technologies, Inc.

CM312 common registers

The utilityModule includes 5 common registers to provide additional information and software

control that is not required for normal COM port operation, but may be helpful in determining the

status of the board and configuring of the board. The following two sections give the location and

definition of the common registers.

Base Address of Common Registers

The utilityModule common registers are located 800h above the address of the first enabled COM

port. That is, assuming that “X” in hex is the first enabled COM port base address, which can be

any of the valid addresses listed in the Com Port Address Table, the base address for the common

registers is “Y” in hex, then,

Y = X + 800h

For example, if the switches of SW4 are set all DOWN position which makes CN3 = 3E8h, CN4 =

2E8h, CN5 = 280h and CN6 = 288h, then according to the algorithm, the common registers base

address (BA) will be the following depending the setting of enable switch SW2 for each serial

port,

If CN3 is enabled then,

BA = 3E8h + 800h = BE8h

Else if CN3 is disabled AND CN4 is enabled then,

BA = 2E8h + 800h = AE8h

Else if CN3 and CN4 are disabled AND CN5 is enabled then,

BA = 280h + 800h = A80h

Else if CN3, CN4 and CN5 are disabled AND CN4 is enabled then,

BA = 288h + 800h = A88 A80h

Else if CN3, CN4, CN5 and CN6 are disabled then,

Common Registers are disabled

End If

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