Introduction - Adaptec AHA-1740A Technical Reference Manual

Chapter Six
Enhanced Mode Firmware Description

Introduction

The Enhanced mode is an interface architecture which allows the AHA-
1740A/1742A/1744 to take full advantage of the EISA bus facilities. It utilizes a dis-
tinct hardware interface control logic, known as the configuration chip. This permits
features such as full 32-bit addressing and the entire EISA register set to be used.
This mode is not compatible with versions of the ASW-1400 series of software manag-
ers before version 3.0. In order to use the Enhanced Mode, the AHA-
1740A/1742A/1744 must be correctly reconfigured by using the configuration utility
described in Chapter Three, Installation. The AHA-1740A/1742A/1744 is not capable
of simultaneous operation in Standard and Enhanced Modes.
Operations using the Enhanced Mode utilize a mailbox interface which is substan-
tially different from the Standard Mode. The principal difference is the use of a sin-
gle mailbox structure which is serviced at a rate that prevents overwriting. The
mailbox structure is described in detail in the section on EISA Expansion Identifiers
in Chapter Four, Hardware Functional Description. The components of the mailbox
are:
zCD0
zCD1
zCD2
zCD3
zCD4
zCD5
zCD6
zCD7
zCD8
zCD9
zCDA
zCDB
Operations using the mailbox begins with the host assembling an Enhanced Control
Block (ECB) in memory. The host then stores the pointer to the ECB in the Mailbox
Out, provided that bit 2 of the SCD7 Status register (MBO empty) is true. Due to the
speed with which the AHA-1740A/1742A/1744 services the mailbox, the MBO will al-
most always be empty.
Mailbox Out Pointer
Mailbox Out Pointer
Mailbox Out Pointer
Mailbox Out Pointer
Attention Register
Enhanced Mode Control Register
Interrupt Status Register
Enhanced Mode Status Register
Mailbox In Pointer
Mailbox In Pointer
Mailbox In Pointer
Mailbox In Pointer
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