1 VER-0.1
Defined as 0x88 (ie. 88hex) for BYTE37 = 0; or 0xc8 for BYTE37 = 1
4th BYTE:
Bit 7 – Defined as 1
Bit 6 to Bit 0 (BYTE36…..BYTE30) – 7 bits of BYTE3 (BYTE37 is in LAST byte)
3rd BYTE:
4th byte
1st BYTE: Bit 7 – Defined as 0
Bit 6 – “DESTINATION BIT”: 0 – information is sent from the PC to the PIP 1 – information is sent from the PIP to the PC
Bit 5 to Bit 0 (INST5…..INST0) – “INSTRUCTION” (6 bits)
The function that is to be performed is defined by the INSTRUCTION code (6 bits). Similarly, if a function is performed via the machine’s keyboard, then the machine sends the appropriate INSTRUCTION code. The instruction codes are defined according to the table below.
2nd BYTE: Bit 7 – Defined as 1
Bit 6 – “REQUEST BIT”: 0 – normal operation
1 – requests the PIP to send current data to the PC
Bit 5 to Bit 0 (BYTE25…..BYTE20) – 2nd byte (6 bits)
If the request bit is set, then the PIP will reply by sending the data related to this instruction to the PC. If not set, then the PIP performs the instruction and replies by returning the same 4 bytes (except for the DESTINATION BIT).
MSB
7
0
1st byte
1
2nd byte
1
3rd byte
1
Communication Protocol
10 Communication Protocol1
This RS-232/RS-485 communication protocol uses four bytes of information as defined below. A null-modem connection (pin 2 and pin 3 crossed; pins 5 connected together) is used to link the PIP unit to the controller unit (for example, PC). The data rate is 9600 baud, with no parity, 8 data bits and 1 stop bit.
When switching (for example, instruction codes 1 and 2), the INPUT (7 bits) is set as the input number, which is to be switched. Similarly, if switching is done via the machine’s front-panel, then these bits are set with the INPUT NUMBER, which was switched. For other operations, these bits are defined according to the table.
Table 10: Protocol Definitions
LSB
| DESTI- | | | INSTRUCTION | | |
| NATION | | | | | | | |
| D | INST5 | INST4 | INST3 | | INST2 | INST1 | INST0 |
| | | | | | | |
| REQUEST | | | | INPUT | | |
| RQ | BYTE25 | BYTE24 | BYTE23 | | BYTE22 | BYTE21 | BYTE20 |
BYTE3
