Sensoray 7429 Manual do Utilizador descarregar pdf (Página 16)

The CRMT and DAV bits are used for communication handshake control as described

in the next section. During a coprocessor reset, CRMT is held low — this prevents the

host from writing to the command register before the coprocessor is ready to commu-

nicate.

The ALARM bit indicates that one or more of the programmable channel limits was ex-

ceeded. This bit will not go to its active state until at least one channel limit value has

been downloaded onto the coprocessor board. The ALARM bit is reset when the co-

processor is reset or when the read alarm flags command is executed (see programming

chapter).

The FAULT bit indicates that the coprocessor self-test failed. This bit is set by either

a system reset or soft reset by command from the host processor. As part of its initial-

ization sequence the coprocessor performs a self-test, clearing the FAULT bit if all

board functions are confirmed to be functioning properly. The self-test consumes ap-

proximately one-half second to complete. Note that the red LED near the top of the co-

processor board reflects the state of the FAULT bit.

Handshake Mechanism

Prior to writing a byte into the command register, the host must test the coprocessor sta-

tus port CRMT bit. When CRMT contains a logic 1, the command register is ready to

accept a new byte. The host should write to the command register only when CRMT

contains a logic 1.

Similarly, the DAV status bit must be tested before reading a byte from the coprocessor

data register. When DAV contains a logic 1 value, a new byte is available in the data

DAV contains a logic 1.

Although these handshake rules are simple, failure to observe them will most likely re-

sult in communication errors.

Sample Drivers

We suggest incorporating procedures into the host processor's 7429 drivers which hide

the communication handshake protocol from higher software layers. Sample QuickBa-

sic drivers are shown below. These drivers are referenced in the programming exam-

ples throughout this manual.

STATUS REGISTER

CRMT ALARM FAULTDAV XXXX

NOT USED

COPR OCESSO R CIRCUIT FA ULT DETEC TED

CH ANNEL ALARM IS SOUND ING

BYTE CAN BE REA D FROM DATA REGISTER

BYTE CAN BE SENT TO COMMA ND REGISTER

D7 D6 D5 D4 D3 D2 D1 D0

1 2 ... 11 12 13 14 15 16 17 18 19 20 21 ... 47 48

Sem comentários

Sensoray 7429 Manual do Utilizador Página 16