Specifications

Communications 3-2
an improper command prompt or address is transmitted. The table below
lists the timeout specification for each command:
Mnemonic Timeout
DI,DO,RD 10 mS
ND See text
All other commands 100 mS
Table 3.1 Response Timeout Specifications.
The timeout specification is the turn-around time from the receipt of a
command to when the module starts to transmit a response.
Data Format
All modules communicate in standard NRZ asynchronous data for-
mat. This format provides one start bit, seven data bits, one parity bit
and one stop bit for each character.
RS-232C
RS-232C is the most widely used communications standard for information
transfer between computing equipment. RS-232C versions of the D1000 will
interface to virtually all popular computers without any additional hardware.
Although the RS-232C standard is designed to connect a single piece of
equipment to a computer, the D1000 system allows for several modules to
be connected in a daisy-chain network structure.The advantages offered by
the RS-232C standard are:
1) widely used by all computing equipment
2) no additional interface hardware in most cases
3) separate transmit and receive lines ease debugging
4) compatible with dumb terminals
However, RS-232C suffers from several disadvantages:
1) low noise immunity
2) short usable distance
3) greater communications delay in multiple-module systems
4) less reliable–loss of one module; communications are lost
5) wiring is slightly more complex than RS-485
6) host software must handle echo characters
Single Module Connection