user manual

Example 2: Monitoring the status of the transmit and receive buffers in RR0 of Channel A.
Register 0 is addressed by default if no register number is written to WR0 first.
mov dx,base ; load base address
add dx,ContA ; add control reg A offset (1)
in ax,dx ; read the status
Example 3: Write data into the transmit buffer of channel A.
mov dx,base ; load base address
out dx,al ; write data in ax to buffer
Example 4: Read data from the receive buffer of channel A.
mov dx,base ; load base address
in al,dx ; write data in ax to buffer
Table 10 SCC read register description.
External/Status interrupt information RR15
Upper byte of baud rate time constantRR13
Lower byte of baud rate time constantRR12
Miscellaneous status parameters RR10
Receive buffer RR8
MSB of frame byte count and FIFO status registerRR7
LSB of frame byte count register RR6
Interrupt Pending bits RR3
Modified Channel B interrupt vector and Unmodified Channel A
interrupt vector
RR2
Special Receive Condition status, residue codes, error conditions RR1
Transmit, Receive buffer statuses and external status RR0
The SCC can perform three basic forms of I/O operations: polling, interrupts, and block
transfer. Polling transfers data, without interrupts, by reading the status of RR0 and then reading
or writing data to the SCC buffers via CPU port accesses. Interrupts on the SCC can be sourced
from the receiver, the transmitter, or External/Status conditions. At the event of an interrupt,
Status can be determined, then data can be written to or read from the SCC via CPU port
accesses. For block transfer mode, DMA transfers accomplish data transfers from the SCC to
memory or from memory to the SCC, interrupting the CPU only when the Block is finished.
Further information on these subjects are found in Sections 4 and 7.
The SCC incorporates additional circuitry supporting serial communications. This
circuitry includes clocking options, baud rate generator (BRG), data encoding, and internal
loopback. The SCC may be programmed to select one of several sources to provide the transmit
MPA-100 User's Manual 6-3