ICS ELECTRONICS 9099, Инструкция по эксплуатации

Страница: 57 / 178

3-11
3
3.3.3 Modbus Error Register
The Modbus Error Register reports a decimal value of the last error detected
with the Modbus message transmission or reported back from the Modbus slave
device. A non-zero value sets bit 6 in the ESR Register. The Modbus Error
Register and bit 6 in the ESR Register are cleared when read by the Modbus
E? command. The *CLS and *RST commands have no affect on this register.
Refer to Table 3-5 for the Modbus Error Register values. The following com-
mands will generate a Service Request when a Modbus error occurs:
*ESE 64 ‘enables ESR bits 6
*SRE 32 ‘enables Status Byte bit 5
*ESR? ‘reads ESR Register bits
E? ‘reads Modbus Error Register
3.3.4 Questionable Registers and Digital Inputs
The Questionable Registers lets the user read bits that report Modbus CRC
errors, Exception message types or a timeout (no response message received).
Bit assignments are shown in Figure 3-1. The Questionable Transition Register
filters the inputs and passes only the enabled state changes to the Questionable
Event Register. The Questionable Event Register bits becomes true (1) when
the positive transition bit is enabled and the associated condition register bit
makes a 0 to 1 transition. When both transitions are selected for the same bit,
the corresponding Questionable Event Register bit sets whenever the digital
input changes state. The Questionable Event Register is cleared when it is read
or by the *CLS command. The Questionable Registers are queried with the
SCPI STATUS branch commands.
The 9099 can be set to monitor the bits in the Questionable Register and gener-
ate a Service Request (SRQ) when they change state. The following example
sets the Questionable Event register to monitor the CRC and Timeout bits by
capturing a positive transition on bits 12 and 13. The decimal value for bit 12
is 4096 and the decimal value for bit 13 is 8192.
STAT:QUES:PTR 12298 ‘enables bits 12 and 13 to set
on a positive transition
Because summing large decimal values is confusing, it is better to use HEX
values that are easier to write. i.e.
STAT:QUES:PTR #h3000 ‘same as 12298 decimal