Synchronous Serial Interface
11-1
CHAPTER
11
SYNCHRONOUS SERIAL INTERFACE
11.1
OVERVIEW
The synchronous serial interface lets the Am186EM and Am188EM microcontrollers
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
Am186EM and Am188EM 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 11-1) 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.
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).
n
The Synchronous Serial Receive Register (SSR) holds data received over the SSI.
Table 11-1
Synchronous Serial Interface Register Summary
Offset
from PCB
Register
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
Summary of Contents for AM186EM
Page 1: ...Am186 EM and Am188 EM Microcontrollers User s Manual...
Page 4: ...iv...
Page 12: ...Table of Contents xii...
Page 62: ...Peripheral Control Block 4 10...
Page 76: ...Chip Select Unit 5 14...
Page 122: ...Timer Control Unit 8 8...
Page 136: ...DMA Controller 9 14...
Page 144: ...Asynchronous Serial Port 10 8...
Page 158: ...Programmable I O Pins 12 6...
Page 186: ...Index I 12...