Reference Manual
PMAC 2 Software Reference
PMAC I-Variable Specification 47
requires that the auto-copying function be enabled.
I67 Modbus TCP Buffer Start Address
Range
$0 – $9FFF
Units
PMAC addresses
Default
0
Remarks
I67 enables the Modbus TCP interface in PMAC software and reports the starting address
of the 256-word Modbus buffer in PMAC memory. To enable the Modbus TCP interface
on the PMAC’s Ethernet port, the following conditions must apply:
1. The Ethernet physical interface must be present
2. The Modbus TCP firmware for the Ethernet processor must be installed
3. V1.17C or newer PMAC firmware must be installed
4. A user buffer of 256 or more words must have been defined with the DEFINE
UBUFFER command
5. I67 must be set to a value greater than 0.
The user can set I67 to any value greater than 0 to enable the Modbus TCP buffer. When
this is done, PMAC will automatically set I67 to the address of the start of the 256-word
Modbus buffer. In most PMAC configurations, this address will be $9F00, so the buffer
will occupy the addresses $9F00 - $9FFF.
A SAVE command must be issued with I67 at a non-zero value in order for the Modbus
TCP buffer to be active after subsequent power-up or reset operations.
I68 Alternate TWS Input Format
Range
0 – 1
Units
None
Default
0
Remarks
I68 controls how the PMAC interprets incoming data on a TWS-format M-variable read
from an ACC-34 or similar serial-interface I/O board. If I68 is set to the default value of 0,
PMAC expects the serial input data on the DAT0 signal line. If I68 is set to 1, PMAC
expects the serial input data on the DAT7 signal line.
The DAT7 line is separated more from the output clock line on the same cable; the use of
DAT7 by setting I68 to 1 and making the appropriate jumper setting on the I/O board
makes it possible to use a longer cable without too much coupling interference between
signals.
On the ACC-34AA, jumper E23 must be connect pins 1 and 2 to support the default setting
of I68 = 0; it must connect pins 2 and 3 to support the setting of I68 = 1. On the ACC-76
and ACC-77 “P-Brain” boards, jumper E1 should be ON to support the default setting of
I68 = 0; jumper E8 should be ON to support the setting of I68 = 1. Older boards of this
class do not support settings of I68 = 1.