X25AM Programming Manual

PTP Applications
X25AM Programming Manual—527201-001
3-11
Mode 2
The Message Control Word
The first word in the WRITE, WRITEREAD, and READ buffers is the MCW. The first
byte specifies the packet type. The second byte specifies the values for the D, Q, and
M bits. The rest of the buffer contains data for each particular packet type. This
information is translated by PTP into the appropriate packet format.
X3PAD packets use the Q bit to distinguish between data packets and control packets.
For detailed information on this topic, see Appendix 4, X3PAD Interface.
READ Request
Your application posts a READ to a subdevice. When the READ completes, the first
word in the file buffer is the MCW. The rest of the buffer contains the contents of one
packet.
READ COUNT will be equal to two (for the MCW) plus the size of the packet
transferred to the application buffer.
Table 3-5. Message Control Word Used for Mode 2
Bit Number Meaning
<0:7> Decimal-value packet code
Code Packet Types
0Data
1 Receive Ready
5 Receive Not Ready
11 Call Request, Incoming Call
15 Call Accepted, Call Connected
19 Clear Request, Clear Indication
23 Clear Confirmation
27 Reset Request, Reset Indication
31 Reset Confirmation
35 Interrupt
39 Interrupt Confirmation
241 Diagnostic
251 Restart Request, Restart Indication
255 Restart Confirmation
<8:12> Must be all 0’s
<13> D bit
<14> Q bit
<15> M bit