USB Channel

Registers in USB channel:

RegNo	Identifier	Memory type	Read Out	Type
0	ReceivedPNETPackets	RAM Read Write	-------	Longinteger
1	SentPNETPackets	RAM Read Write	-------	Longinteger
2
3	SnoopEnabled	RAM Read Write		Boolean
4	DisablePNETCommunication	RAM Read Write		Boolean
5	Reserved	RAM Read Write		Byte
6
7
8
9
10
11
12
13
14	Guid	PROM Read only	-------	String
15	ChError	RAM Read Write	-------	Record

RegNo. 0: ReceivedPNETPackets

SentBytes:

LongInteger;

This register shows how many P-NET packets have been received from the PC.

RegN o 1: SentPNETPackets

ReceivedBytes:

LongInteger;

This register shows how many P-NET packets have been sent to the PC.

RegNo 3: SnoopEnabled

SnoopEnabled:

Boolean; (* Factory setting = False *)

This register is used to enable the PD 3950 snoop facility. The snoop software will automatically control this setting.

RegNo 4: DisablePNETCommunication

DisablePNETCommunication:

Boolean; (* Factory setting = False *)

Enabling this flag puts the P-NET Interface into passive mode, where no load, store or sync packets are sent. As an exeption to the standard P-NET rules, it is permitted to use any P-NET node address between 1-125, without risking a node address conflict on the network. This feature is mainly used together with the built in snoop functionality within the module.

RegNo 5: Reserved

Reserved:

Byte;

Reserved for future use.

RegNo 14: GUID

Guid:

String[22];

Each channel type is identified by means of a unique GUID. The value of GUID for the USB channel is: PD/551316-01.

RegNo 15: ChError

Record
	His:	Bit16;
	Act:	Bit16;
End;

There are two sets of error bits, actual and historical. The actual error bits reflect the current situation and will automatically follow any change.

The historical error bits reflect the history and have the purpose of holding sporadic errors. The historical error bits are set together with the corresponding actual bits. They remain set after a read, so each individual bit must be cleared manually, via P-NET. Only the bits where the corresponding actual bit is false can be cleared.

The “His data error” bit in the P-NET response is set if any historical bit is true.

The “Act data error” bit in the P-NET response reflects the validity of the data in the response. An error in registers involved in calculating the result gives “Act data error”.

0: Program_storage_fault

1: RAM_storage_fault

2: InternalReset

3: ExternalReset

4: ModuleError

5: Not used

6: Not used

7: Not used

8: P-NET_Gateway_Service_Connection_Error

9: Not used

10: Not used

11: Not used

12: Not used

13: Not used

14: Not used

15: Not used

Bits 0,1 and 4 will cause Act error in the P-NET response on access to all variables.

Bit 0: Program_storage_fault is set if the self-test finds an error in the program memory.

Bit 1: RAM_storage_fault is set if the self-test finds an error in the data memory (RAM).

Bit 4: ModuleError is set if a module error occurs.

Bits 2, 3 and 8 will cause His error in the P-NET response on access to all variables.

Bit 2: InternalReset is set if a reset is caused by a power failure, or if the power has been disconnected (only a His error).

Bit 3: ExternalReset is set if a reset is caused by writing 255 to Reset, via P‑NET (only a His error).

Bit 8: P-NET_Gateway_Service_Connection_Error is set if the module fails to connect to the service. This error will appear if the service is stopped or removed.