The end of the NCMDSTRB will initiate the DMA cycle to transfer
the data words from the data buffer memory to the subsystem. The
first word received is enabled onto T0-T15 and the signal
NDATAST is pulsed low. This sequence is repeated for each data
word that was received.
Error Conditions
Action taken by device
1. Invalid command.
No response.
Command ignored.
2. Command followed by
another word.
No status response.
Set message error.
Sequence terminated.
Error Conditions
Action taken by device
1. Invalid command.
No response.
Command ignored.
3. Broadcast address.
No status response.
Set message error.
Set broadcast.
2. Invalid data word.
No status response.
Set message error.
Sequence terminated.
Sequence terminated.
4. Too few NSSTRB from
subsystem.
Message truncated.
3. Non contiguous data.
4. Too few data words.
5. Too many data words.
No status response.
Set message error.
Sequence terminated.
5.Too many NSSTRB from Bit 1 of BIT register set.
subsystem.
Too many data words will
not be transmitted.
No status response.
Set message error.
Sequence terminated.
Note: Sequence terminated - termination will take place before
signal NCMDSTRB becomes active, therefore no transfers to /
from subsystem will occur.
No status response.
Set message error.
Set broadcast.
BC TO RT TRANSFER
Sequence terminated.
RX
CMD
Note: Sequence terminated - termination will take place before
signal NCMDSTRB becomes active, therefore no transfers to /
from subsystem will occur.
STATUS
DATA DATA
DATA
*
If a valid command is received to receive up to 32 data words and
the second word is another command word then an RT to RT
transfer has been set up (see RT to RT transfer).
RT TO RT TRANSFER
All valid data words received are stored in the data buffer memory
until message validation is complete after which the device will
respond with Status.
RX
TX
STATUS
STATUS
DATA
CMD CMD
*
*
To initiate an RT to RT transfer the Bus Controller will send a
receive command to RTA followed contiguously by a transmit
command to RTB.
If the command was a broadcast the status transmission will be
suppressed and the broadcast bit in the status register set.
Data words are also available on T0-T15 as they are received
indicated by signal NDATA.
RTB will respond with status and contiguous data (see RT to BC
transfer).
Only after the message has been completely validated will the data
be transferred to the subsystem in a single burst at 500 nS per
word. This ensures that only complete validated messages are
transferred to the subsystem.
RTA (the receiving terminal) will receive the status and data
transmitted by RTB and store the received data in the data buffer
memory until the entire RT to RT transfer has been validated, after
which it will respond with its own status provided it was not a
broadcast command, in which case the status transmission will be
suppressed and the broadcast bit set. It will then transfer the data
to the subsystem (see BC to RT transfer).
When a complete validated message is stored in the data buffer
memory the signal NCMDSTRB goes low for 8.5 uS synchronized
to the 1 MHZ clock indicating that a completely validated message
has been received. The receive Command word appears on T0-T15
at this time.
The error detection for the transmitting terminal will be the same
as for RT to BC transfer. The error detection for the receiving
terminal is as follows:-
If the Busy bit of the Status is set the sequence will terminate after
NCMDSTRB.
9
SCDCT2578 REV B 3/11/98
AEROFLEX [ AEROFLEX CIRCUIT TECHNOLOGY ]
