Interfacing the Am188
TM
EM Controller to the
DSLAC
TM
/QSLAC
TM
Devices Using the SSI
Application Note
The purpose of this application note is to show the user how to interface the Am188鈩M micro-
controller to the DSLAC鈩?and QSLAC鈩?devices using the Synchronous Serial Interface (SSI).
These techniques are not restricted to the Am188EM microcontroller; other members of the
Am186鈩?microcontroller family with SSI ports can be interfaced in a similar fashion.
BACKGROUND
Traditionally, line cards (if they had a processor at all)
used a simple, inexpensive 8-bit microcontroller. How-
ever, as the number of lines per card increases, 16-bit
controllers like the Am188鈩M microcontroller be-
come more attractive for several reasons:
s
Over time 16-bit controller costs have decreased
s
More peripheral functions are integrated, reducing
external components counts
s
Newer, smaller packaging options are available
s
16-bit controllers generally offer larger address
spaces
These reasons, combined with the availability of supe-
rior, low-cost development tools like Microsoft & Bor-
land C, r educ e tim e-to -ma rk et and lo ng- term
maintenance costs.
The SLAC鈩?device connects to the host processor
through a 3-pin serial interface. While this interface is
used primarily to initialize the SLAC device, several
critical functions of the SLIC鈩?device can be moni-
tored through the serial interface; therefore, it may be
necessary to make the interface as fast as possible.
Using the SSI port of the Am188EM microcontroller re-
duces software overhead making the interface much
faster.
The serial Microprocessor Interface (MPI) of the
DSLAC鈩?and QSLAC鈩?devices pre-dates most鈥攊f
not all鈥攐f today鈥檚 industry standard serial interfaces
ports, including the Synchronous Serial Interface (SSI)
port of the Am188EM microcontroller. Because these
two serial interfaces (MPI and SSI) were not designed
to be compatible, it takes a little effort to make them
work together. This application note attempts to show
that it is worth the effort and explains how to do it.
In most line-card designs, the only cost effective alter-
native is to interface to the processor鈥檚 PIOs and ma-
nipulate the MPI signal lines directly from software.
While this is a perfectly acceptable approach鈥攅ven
desirable in some cases鈥攖he use of the SSI port can
greatly reduce software overhead and code space.
FURTHER REFERENCES
The remainder of this application note assumes at least
a passing familiarity with the chips involved; the
Am188EM microcontroller, the Am79C02 DSLAC fam-
ily, and the Am79Q02 QSLAC family. If additional de-
tails are needed, the following literature is available
from AMD:
Am186鈩M/EMLV and Am188鈩M/EMLV
Microcontrollers Data Sheet
, order #19168
Am186鈩M and Am188鈩M Microcontrollers
User鈥檚 Manual,
order #19713
Am79C02/03/031(A) DSLAC鈩?Device Data Sheet
,
order #18503
Am79Q02/021/031 QSLAC鈩?Device Data Sheet,
Available through your local AMD sales office
AMD鈥檚 complete line of line card devices are found in
the
Linecard Products for the Public Infrastructure Mar-
ket Data Book
, Publication #18503.
MPI HARDWARE OVERVIEW
The QSLAC and DSLAC devices have very similar
MPIs; both are serial, master/slave-type interfaces. Dif-
ferences between the two devices are described in the
following paragraphs. A system or line card micropro-
cessor is the master and the interface is designed so
that multiple slaves (i.e. SLAC devices) can be at-
tached to a single master鈥檚 MPI bus.
The MPI signals, like most digital buses, consist of
three types of signals:
s
Clock/Control
s
Address
s
Data
The data line (DIO) is a bidirectional, three-state serial
bus. The Am79C02 has separate data in (Din) and data
out (Dout) pins that can be strapped together to look
Publication# 21728 Rev: A Amendment/0
Issue Date: May 1997
This document contains information on a product under development at Advanced Micro Devices. The information
is intended to help you evaluate this product. AMD reserves the right to change or discontinue work on this proposed
product without notice.
1
2
3
4
5
6
7
8
9
10
11
