Motorola MC68824 User Manual page 66

Issue the OFFLINE Command
Check for CRC/Underrun Errors (Bit 1 of the Command Result area will be set if such errors
occurred.)
Check the FD Confirmation Word for Each Transmitted Frame
NOTE
In order to check for command completion, the host must clear the done bit in CPA
status word before issuing a command to the TBC.
3.6.5 RECEIVER TEST Command
The receiver test is used by the host processor to check the path from the receiver to the RX
queue in memory. The transmitter transmits a predefined pattern partitioned into frames of up
to 33 bytes in length. The pattern of the frame is user definable and is loaded by the host through
CPA VALO. This pattern will be transmitted between the SD and FCS (CRC) of frames from the
least significant byte to the most significant byte. However, care should be taken not to create
an RWR pattern. For this test to run, it is required that the TBC generate the CRC, therefore the
TCDS bit should be left disabled using the SET MODE 3 command (see 3.3.3 SET MODE 3
Command). The PTP register has a different format in this test than in normal mode as shown.
PTP register format for the receive test:
D e B A
3
p
I
p
I
p
Where:
m
=
Frame's length - number of bytes between the start delimiter up to but not including the
CRC (FCS) minus two (2).
b
=
Number of preamble octets between frames minus one (1).
p
=
Pattern of preamble octet
The command confirmation bit is set by the TBC upon completion of the OFFLINE command and
the status is placed in the command return area. Status is given on every frame in the FD (class
6) as in normal frame reception. In order to determine success or failure of the test, the host
processor checks the received frames against what was sent in CPA VALO.
NOTES
Using a 1: 1 ratio of the serial clock to the system clock, an overflow is expected after
approximately every third frame. To reduce the number of overruns when running this
test, it is recommended to use 16 words as the minimum data buffer length, and to
allocate one buffer descriptor per frame descriptor.
The following routine may be used to perform the receiver test:
Prepare the Initialization Table
Issue RESET Command
Wait until Semaphore Register is 'FF'
Initialize the Interrupt Vector Register
MC68824 USER'S MANUAL MOTOROLA
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