Solartron Mobrey 3595 4C, User Manual

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Programming the 3595 4C Interface card 3595 4C User Manual Part One
3-8
35952350 (CH03/AA)
3.3.2 Transmitting a command message
To make an IMP do something, the Host PC sends it a command message. This is loaded into RAM Page 1 ,
which can hold up to 256 bytes . (Details of the IMP commands are given in Part 2 of this manual.)
To control message transmission, the Host PC uses the TRANSMIT REGISTERS (Section 3.4.8, Page 3-13).
These allow the Host PC to:
•
specify the number of bytes to be transmitted,
•
specify the address of the IMP to which the message is to be sent,
•
communicate with the 4C Interface card regarding:
— transmission requests,
— transmission errors,
— transmission busy, and
— ‘break’ character transmission (for resetting locally powered IMP devices).
•
specify whether it wants to be interrupted at the end of transmissions.
3.3.3 Receiving measurement results
Measurement data is received only from those IMP devices selected in the POLL TABLE (Section 3.4.6,
Page 3-12). The 4C Interface card polls each of these IMP devices in turn.
When an IMP has data ready to send back to the 4C Interface card, it responds to a poll by placing the data
on the S-Net. If the data is received successfully, the card places it in the RAM Page for measurement
results relating to the IMP. The 4C Interface card then sets the Data Ready (DR) bit and Data Offset for
that IMP and stream, in the
RECEIVE TABLE (Section 3.4.9, Page 3-15). If the Data Offset in this table is
multiplied by four, it gives the address with the IMP’s data page at which the data is to be found.
When measurement data has been read by the PC, the relevant entry in the RECEIVE TABLE should be
cleared. This allows the 4C Interface card to receive further measurement data from the IMP and stream.
Data can be received on four streams from each IMP and should reception fail on any stream then the 4C
Interface card tries three more times to receive data before reporting an error. The card reports errors by
setting the Receive Data Error bit (RXE) in the RECEIVE TABLE for each active stream of the IMP that is
being polled.
For all IMP devices, the Host PC can enable interrupts on selected data streams by setting the relevant bits
in the RECEIVE INTERRUPT TABLE (Section 3.4.10, Page 3-16). On data streams, for which interrupts
are enabled, an interrupt is generated by the 4C Interface card either when data is successfully received or
when a ‘receive error’ is reported.
3.3.4 Using interrupts
The 4C Interface card is able to interrupt the Host PC for the following things:
•
transmit complete,
•
calendar access granted, and
•
measurement data received, for each of four streams on up to 50 IMP devices.
Whilst any of these conditions exists, and an interrupt is enabled, the 4C Interface card continues to
interrupt the PC. Therefore, special processing of interrupts may be necessary if the Host PC is able to
service
all sources of interrupts, and not just one or two busy ones.
It is recommended that, once a source of interrupt has gained the attention of the Host PC, any further
interrupts from the same source are inhibited until other equally important interrupts have been attended to.