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2-30
Functional Description
For send operations, the End of DMA bit is set when the DMA finishes
its transfer, but the SCSI transfer may still be in progress. If connected
as a target, REQ/ and ACK/ should be sampled until both are false. In
the SYM53C040 SCSI core, the Last Byte Sent (bit 7 of the
register) may be sampled to determine when the last
byte was transferred.
2.10.2.2 SCSI Bus Reset Interrupt
The SCSI core generates an interrupt when the RST/ signal transitions
to asserted. The device releases all bus signals within a bus clear delay
(800 ns) of this transition. This interrupt also occurs after setting the
Assert RST/ bit (bit 7 of register
).
Note:
The RST/ signal is not latched in bit 7 of the
register and may not be active when
this bit is read. For this case, the Bus Reset interrupt may
be determined by default.
2.10.2.3 Parity Error Interrupt
An interrupt is generated for a received parity error if the Enable Parity
Check bit (bit 5) and the Enable Parity Interrupt bit (bit 4) are set in the
register (
). Parity is checked during a read of the
register (
) and during a DMA receive
operation. A parity error can be detected without generating an interrupt
by disabling the Enable Parity Interrupt bit and checking the Parity Error
flag (bit 5 in register 0xFC05).
2.10.2.4 Bus Phase Mismatch Interrupt
The SCSI phase lines are the I_O/, C_D/, and MSG/ bus signals. These
signals are compared with the corresponding bits in the
register: Assert I_O/ (bit 0), Assert C_D/ (bit 1), and Assert MSG/
(bit 2). The comparison occurs continually and is reflected in the Phase
Mismatch bit (bit 3) of the
register (
). If the
DMA Mode bit (bit 1 in register 0xFC02) is active and a phase mismatch
occurs when REQ/ transitions from HIGH to LOW, an interrupt (IRQ) is
generated.
A phase mismatch prevents the recognition of REQ/ and removes the
chip from the bus during an initiator send operation. DB0/ through DB7/
Содержание Symbios SYM53C040
Страница 12: ...xii Preface...
Страница 90: ...4 18 SCSI and DMA Registers...
Страница 98: ...5 8 SFF 8067 Registers...
Страница 110: ...6 12 Two Wire Serial Registers...
Страница 126: ...7 16 Miscellaneous Registers...
Страница 160: ...8 34 System Registers...
Страница 184: ...9 24 Electrical Characteristics...
Страница 194: ...A 10 Register Summary...
Страница 214: ......