C167CS datasheet(295/517 Pages) INFINEON

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C167CS

Derivatives

The High-Speed Synchronous Serial Interface

User’s Manual

12-12

V2.0, 2000-07

12.4

Port Control

The SSC uses three pins of Port 3 to communicate with the external world. Pin P3.13/

SCLK serves as the clock line, while pins P3.8/MRST (Master Receive/Slave Transmit)

and P3.9/MTSR (Master Transmit/Slave Receive) serve as the serial data input/output

lines.The operation of these pins depends on the selected operating mode (master or

slave). In order to enable the alternate output functions of these pins instead of the

general purpose IO operation, the respective port latches have to be set to ‘1’, since the

port latch outputs and the alternate output lines are ANDed. When an alternate data

output line is not used (function disabled), it is held at a high level, allowing IO operations

via the port latch. The direction of the port lines depends on the operating mode. The

SSC will automatically use the correct alternate input or output line of the ports when

switching modes. The direction of the pins, however, must be programmed by the user,

as shown in the tables. Using the open drain output feature helps to avoid bus contention

problems and reduces the need for hardwired hand-shaking or slave select lines. In this

case it is not always necessary to switch the direction of a port pin. Table 12-1

summarizes the required values for the different modes and pins.

Note: In Table 12-1, an ‘x’ means that the actual value is irrelevant in the respective

mode, however, it is recommended to set these bits to ‘1’, so they are already in

the correct state when switching between master and slave mode.

Table 12-1

SSC Port Control

Master Mode

Slave Mode

Function Port Latch

Direction

Function Port Latch

Direction

SCLK

Serial

Clock

Output

P3.13 = ‘1’

DP3.13 = ‘1’ Serial

Clock

Input

P3.13 = ‘x’

DP3.13 = ‘0’

MTSR

Serial

Data

Output

P3.9 = ‘1’

DP3.9 = ‘1’

Serial

Data

Input

P3.9 = ‘x’

DP3.9 = ‘0’

MRST

Serial

Data

Input

P3.8 = ‘x’

DP3.8 = ‘0’

Serial

Data

Output

P3.8 = ‘1’

DP3.8 = ‘1’

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