Measurement-computing PC104-AC5 Manual de usuario descargar pdf (Pagina 11)

In summary form, the registers and their function are listed on the following table.

Within each register are eight bits which may constitute a byte of data or eight

individual bit set/read functions.

Table 3-1. Board Register Functions

Configure I/ONone. BASE +3

1st Port C Output1st Port C InputBASE +2

1st Port B Output1st Port B InputBASE +1

1st Port A Output1st Port A Input BASE +0

WRITE FUNCTIONREAD FUNCTIONADDRESS

3.2 DIGITAL DATA REGISTERS

Port A

Base Address + 0

A0A1A2A3A4A5A6A7

01234567

Port B Data

Base Address +1

B0B1B2B3B4B5B6B7

01234567

Ports A & B may be programmed as input or output. Each is written to and read from

in bytes, but for control and monitoring, use individual bits.

When using bit set/reset and bit read functions, unwanted bits must be masked out of

reads and ORed into writes.

Port C Data

Base Address +2

CL0CL1CL2CL3CH0CH1CH2CH3

C0C1C2C3C4C5C6C7

01234567

Port C may be used as one 8-bit port of either input or output, or it may be split into

two 4-bit ports which may be independently input or output. The notation for the

upper 4-bit port is CH3 - CH0, and for the lower, CL3 - CL0.

Although it may be split, every read and write to port C carries eight bits of data so

unwanted information must be ANDed out of reads, and writes must be ORed with the

current status of the other port.

1 2 ... 6 7 8 9 10 11 12 13 14 15 16 ... 23 24

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Measurement-computing PC104-AC5 Manual de usuario Pagina 11