Function 0x64: Read Interface Record

This function reads the driver's interface record and copies it into the buffer passed by the SNALink. The buffer must be allocated by the SNALink prior to making this call.

Parameters

IRP.System.Buffer
Interface Record Address (IN) — a 32-bit pointer to the driver's interface record area.

The interface record format is as follows:
Description Type
Received Frames int
Transmit Buffer Space int
Status Events int
Input V.24 Status UCHAR
Output V.24 Status UCHAR
Statistics Counters int[11]

Bit
number
V.24 circuit name Circuit
number
RS-232C pin
7 - 5 Reserved 142 25
4 Test Indicator 125 22
3 Calling Indicator 125 22
2 RLSD (commonly DCD) 109 8
1 Data Set Ready (DSR) 107 6
0 Ready For Sending (CTS) 106 5

Bit
number
V.24 circuit name Circuit
number
RS-232C pin
7 - 5 Reserved
4 Maintenance Test 140 18
3 Select Standby 116 11
2 Data Signal Rate Selector 111 23
1 Data Terminal Ready (DTR) 108/2 22
0 Request to Send (RTS) 105 4

Note that the driver will raise and lower RTS as necessary while transmitting, reflecting the state of RTS in the output V.24 status field. The application should not, therefore, try to manipulate RTS.

Counter 1 Frames received with incorrect CRC.
Counter 2 Frames larger than the maximum size received.
Counter 3 Frames smaller than 32 bits received.
Counter 4 Frames received that are not a multiple of 8 bits.
Counter 5 Aborted frames received.
Counter 6 Transmitter underruns.
Counter 7 Receiver overruns.
Counter 8 RLSD drops in mid-reception.
Counter 9 CTS drops in mid-transmission.
Counter 10 DSR drops.
Counter 11 Hardware failures (adapter or modem).

Remarks

The interface record provides a fast mechanism to use to decide whether a frame can be transmitted, whether there are any frames to be received, and so on. The driver maintains this information. Each time the SNALink requires this information, it calls Read Interface Record to get a copy of the current interface record. After each call, the driver clears the statistics counters in its own interface record. The V.24 status and transmit and receive data information are unchanged.