S1R72104 Technical Manual
Rev.1.1
EPSON
17
7.3.14 FIFO Data (FIFODATA) R/W
This is a register to access SCSI-FIFO from CPU.
7 6 5 4 3 2 1 0
FD7
FD6 FD5 FD4 FD3
FD2 FD1 FD0
12h
7.3.15 Non DMA Transfer Size (NDMASIZ) R/W
Sets the bytes number of data transferred in Non-DMA mode (the message and command phases).
In Read mode, the register allows to read out the size of data yet to be transferred.
7 6 5 4 3 2 1 0
NSZ7 NSZ6 NSZ5 NSZ4 NSZ3
NSZ2 NSZ1 NSZ0
13h
7.3.16 SCSI Command (COMMAND) R/W
Sets SCSI control commands.
7 6 5 4 3 2 1 0
CMD7 CMD6 CMD5 CMD4 CMD3 CMD2 CMD1 CMD0
14h
Refer to [7.4 SCSI Control Commands] as for the details of each of them.
7.3.17 DMA Control (DMACTL) R/W
7 6 5 4 3 2 1 0
- -
-
- -
-
FIFO
DTGO
17h
DMA
TRANSFER
GO
FIFO CONTROL
BIT7-2 RESERVED
BIT1 FIFO CONTROL
Setting this bit and DTGO to HIGH at the same time causes DMA transfer using FIFO, without using port interface.
CPU must write data in FIFO according to FULL/EMPTY status of FIFO. Alternately, it may first write data in FIFO
and set HIGH in this bit and DTGO, then make control with remaining data and FULL/EMPTY. Though, CPU may
not access FIFO reversely against the direction of transfer.
This bit is used together with SCSI command for DMA Data In/Out. Note that FIFO is cleared when SCSI phase is
switched to the data phase if DMA Data In/Out command was issued without setting this bit.
FIFO is not cleared if DMA Data In/Out command is issued after this bit was set. So it is possible that FIFO has data
written beforehand.
BIT0 DMA TRANSFER GO
Setting this bit to HIGH causes DMA transfer to start. Setting it to HIGH before entering the data phase is allowed,
too.
7.3.18 DMA Transfer Byte Count 2 (DTBC2) R/W
Sets the most significant byte of the byte-length (3 bytes) for DMA transfer.
Setting of DTBC2 to 0 allows the setting of the byte-length up to FFFFFFh.
7 6 5 4 3 2 1 0
DBC23 DBC22 DBC21 DBC20 DBC19 DBC18 DBC17 DBC16
19h
7.3.19 DMA Transfer Byte Count 1 (DTBC1) R/W
Sets the second byte of the byte-length (3 bytes) for DMA transfer.
7 6 5 4 3 2 1 0
DBC15 DBC14 DBC13 DBC12 DBC11 DBC10 DBC9 DBC8
1Ah