LSI LSI53C895A, Technical Manual

Page: 148 / 364

4-40 Registers
REQ SREQ/ Status 7
ACK SACK/ Status 6
BSY SBSY/ Status 5
SEL SSEL/ Status 4
ATN SATN/ Status 3
MSG SMSG/ Status 2
C_D SC_D/ Status 1
I_O SI_O/ Status 0
Register: 0x0C
DMA Status (DSTAT)
Read Only
Reading this register clears any bits that are set at the time the register
is read, but does not necessarily clear the register in case additional
interrupts are pending (the LSI53C895A stacks interrupts). The DIP bit
in the
Interrupt Status Zero (ISTAT0) register is also cleared. It is possible
to mask DMA interrupt conditions individually through the DMA Interrupt
Enable (DIEN) register.
When performing consecutive 8-bit reads of the DSTAT, SCSI Interrupt
Status Zero (SIST0) and SCSI Interrupt Status One (SIST1) registers (in
any order), insert a delay equivalent to 12 CLK periods between the
reads to ensure that the interrupts clear properly. See
Chapter 2,
“Functional Description,” for more information on interrupts.
DFE DMA FIFO Empty 7
This status bit is set when the DMA FIFO is empty. It is
possible to use it to determine if any data resides in the
FIFO when an error occurs and an interrupt is generated.
This bit is a pure status bit and does not cause an
interrupt.
7 6 5 4 3 2 1 0
DFE MDPE BF ABRT SSI SIR R IID
1 0 0 0 0 0 x 0