am53c94 Advanced Micro Devices, am53c94 Datasheet - Page 27

• Manufacturer Part Number: am53c94
• Description: High Performance Scsi Controller
• Manufacturer: Advanced Micro Devices

Current FIFO/Internal State Register (07H) Read
This register has two fields, the Current FIFO field and
the Internal State field.
CFISREG – Bits 7:5 – IS 2:0 – Internal State 2:0
The Internal State Register (ISREG) tracks the progress
of a sequence-type command.
The IS 2:0 bits are duplicated from the IS 2:0 field in the
Internal State Register (ISREG) in the normal mode. If
the device is in the test mode, IS 0 is set to indicate that
the offset value is non zero. A non zero value indicates
Synchronous Offset Register (07H) Write
The Synchronous Offset Register (SOFREG) contains
a 4-bit count of the number of bytes that can be sent to
(or received from) the SCSI bus without an ACK (or
REQ). Bytes exceeding the threshold will be sent one
byte at a time (asynchronously). That is, each byte will
require an ACK/REQ handshake. To set up an asyn-
chronous transfer, the SOFREG is set to zero. The
SOFREG is set to zero after a hard or soft reset.
Current FIFO/Internal State Register
CFISREG
Synchronous Offset Register
SOFREG
RES
IS2
7
0
7
x
RES
IS1
6
0
6
x
RES
IS0
5
0
5
x
P R E L I M I N A R Y
Am53C94/Am53C96
RES
CF4
4
0
4
x
SO3
CF3
3
3
0
0
that synchronous data transfer can continue. A zero
value indicates that the synchronous offset count has
been reached and no more data can be transferred until
an acknowledge is received.
CFISREG – Bits 4:0 – CF 4:0 – Current FIFO 4:0
The CF 4:0 bits are the binary coded value of the num-
ber of bytes in the FIFO. These bits should not be read
when the device is transferring data since this count
may not be stable.
SO2
SOFREG – Bits 7:4 – RES – Reserved
SOFREG – Bits 3:0 – SO 3:0 – Synchronous Offset
3:0
The SO 4:0 bits are the binary coded value of the num-
ber of bytes that can be sent to (or received from) the
SCSI bus without an ACK (or REQ) signal.
CF2
2
0
2
0
CF1
SO1
1
0
1
0
Address: 07
Address: 07
Type: Read
Type: Write
CF0
SO0
0
0
0
0
H
H
Current FIFO 4:0
Internal State 2:0
Synchronous Offset 3:0
Reserved
Reserved
Reserved
Reserved
16506C-27
16506C-26
AMD
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