LSI LSI53C895A, Technical Manual

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SCSI Registers 4-37
is also possible to program these signals as live inputs
and sense them through a SCRIPTS register to register
Move Instruction. GPIO4 may be used to enable or
disable V
PP
, the 12 Volt power supply to the external flash
memory. This bit powers up with the power to external
memory disabled. GPIO[3:0] default as inputs and GPIO4
defaults as an output pin. When configured as inputs, an
internal pull-down is enabled for GPIO[4:2]. For
GPIO[1:0], internal pull-ups are enabled.
LSI Logic software uses the GPIO[1:0] signals to access
serial EEPROM. GPIO1 is used as a clock, with the
GPIO0 pin serving as data.
LSI Logic software also reserves the use of GPIO[4:2]. If
there is a need to use GPIO[4:2] please check with
LSI Logic for additional information.
Register: 0x08
SCSI First Byte Received (SFBR)
Read/Write
This register contains the first byte received in any asynchronous
information transfer phase. For example, when a LSI53C895A is
operating in the initiator mode, this register contains the first byte
received in the Message-In, Status phase, and Data-In phases.
When a Block Move instruction is executed for a particular phase, the
first byte received is stored in this register, even if the present phase is
the same as the last phase. The first byte received for a particular input
phase is not valid until after a MOVE instruction is executed.
This register is also the accumulator for register read-modify-writes with
the SFBR as the destination. This allows bit testing after an operation.
The SFBR is not writable using the CPU, and therefore not by a Memory
Move. However, it can be loaded using SCRIPTS Read/Write operations.
To load the SFBR with a byte stored in system memory, the byte must
first be moved to an intermediate LSI53C895A register (such as a
SCRATCH register), and then to the SFBR.
7 0
1B
0 0 0 0 0 0 0 0