AMD Am186TMER ユーザーズマニュアル
Synchronous Serial Interface
12-1
CHAPTER
12
SYNCHRONOUS SERIAL INTERFACE
12.1
OVERVIEW
The synchronous serial interface enables the Am186ER and Am188ER microcontrollers
to communicate with application-specific integrated circuits (ASICs) that require
programmability but are short on pins. The four-pin interface permits half-duplex,
bidirectional data transfer at speeds of up to 20 Mbit/s with a 40-MHz CPU clock.
to communicate with application-specific integrated circuits (ASICs) that require
programmability but are short on pins. The four-pin interface permits half-duplex,
bidirectional data transfer at speeds of up to 20 Mbit/s with a 40-MHz CPU clock.
Unlike the asynchronous serial port, the SSI operates in a master/slave configuration. The
Am186ER and Am188ER microcontrollers operate as the master port.
Am186ER and Am188ER microcontrollers operate as the master port.
The SSI interface provides four pins for communicating with system components: two
enables (SDEN0 and SDEN1), a clock (SCLK), and a data pin (SDATA). Five registers
(see Table 12-1) are used to control and monitor the interface.
enables (SDEN0 and SDEN1), a clock (SCLK), and a data pin (SDATA). Five registers
(see Table 12-1) are used to control and monitor the interface.
n
The Synchronous Serial Status register (SSS) reports the current port status.
n
The Synchronous Serial Control register (SSC) sets the port clock rate and controls the
enable signals.
enable signals.
n
There are two data transmit registers—the Synchronous Serial Transmit 0 register
(SSD0) and the Synchronous Serial Transmit 1 register (SSD1)—but data is transmitted
and received over a single pin (SDATA).
(SSD0) and the Synchronous Serial Transmit 1 register (SSD1)—but data is transmitted
and received over a single pin (SDATA).
n
The Synchronous Serial Receive Register (SSR) holds data received over the SSI.
Table 12-1
Synchronous Serial Interface Register Summary
Offset from
PCB
PCB
Register
Mnemonic
Mnemonic
Register Name
10h
SSS
Synchronous Serial Status
12h
SSC
Synchronous Serial Control
14h
SSD1
Synchronous Serial Transmit 1
16h
SSD0
Synchronous Serial Transmit 0
18h
SSR
Synchronous Serial Receive