BCRTM-32
7.4 Bus Controller Operational Sequence
The following is a general description of the typical
behavior of the BCRTM as it processes a message in the
BC mode.
The user starts BC operation by writing a “1” to Register
0, Bit 0.
• Command Block DMA - the following occurs
immediately after Bus Controller startup:
DMA arbitration (BURST)
Control Word read
Command Word 1 read (from third location
of Command Block)
Data List Pointer read
A. For BC-to-RT Command Blocks:
The BCRTM transmits the Command Word.
• Data Word DMA
DMA arbitration
Data Word read (starting at Data List Pointer
address, incremented for each successive
word)
The BCRTM transmits the Data Word. Data Word DMAs
and transmissions continue until all Data Words are
transmitted.
• Status Word DMA
The BCRTM receives the RT Status Word.
DMA arbitration
Status Word write (to sixth location of
Command Block)
B. For RT-to-BC Command Blocks:
The BCRTM transmits the Command Word.
• Status Word DMA
The BCRTM receives the RT Status Word.
DMA arbitration
Status Word write (to sixth location of
Command Block)
The BCRTM receives the first Data Word.
• Data Word DMA
DMA arbitration
Data Word write (starting at Data List
Pointer address, incremented for each
successive word)
Data Word receptions and DMAs continue until all Data
Words are received.
C. For RT(A)-to-RT(B) Command Blocks:
The BCRTM transmits Command Word 1 to RT(B).
• Command Word 2 DMA
DMA arbitration
Command Word 2 read (from fourth location
of Command Block)
The BCRTM transmits Command Word 2 to RT(A).
The BCRTM receives the RT Status Word from RT(A).
• Status Word DMA for RT(A) Status Word
DMA arbitration
Status Word write (to sixth location of
Command Block)
The BCRTM receives the first Data Word
• Data Word DMA (only if the BCRTM is enabled to
monitor the RT-to-RT message).
DMA arbitration
Data Word write (starting at Data List Pointer
address, incremented for each successive
word)
Data Word receptions and DMAs continue until all Data
Words are received.
The BCRTM receives the RT Status Word from RT(B).
• Status Word DMA for RT(B) Status Word
DMA arbitration
Status Word write (to seventh location of
Command Block)
RT
BC
RESPONSE
Q?
RTRT
POLLING RESPONSE REGISTER
(RT STATUS WORD)
POLLING COMPARE WORD
(SET BY CPU)
Figure 16. Polling Operation
