peb20534 Infineon Technologies Corporation, peb20534 Datasheet - Page 120

• Manufacturer Part Number: peb20534
• Description: Dma Supported Serial Communication Controller With 4 Channels
• Manufacturer: Infineon Technologies Corporation

Figure 36
Note: The shift direction applies to MSB-first operation as well as to LSB-first operation.
The data output pins MRST of all slave devices are connected together onto the one
receive line in this configuration. During a transfer each slave shifts out data from its shift
register. There are two ways to avoid collisions on the receive line due to different slave
data:
1. Only one slave drives the line, i.e. enables the driver of its MRST pin. All the other
2. The slaves use open drain output on MRST. This forms a Wired-AND connection.
Data Sheet
slaves have to program their MRST pins to input. So only one slave can put its data
onto the master's receive line. Only receiving of data from the master is possible. The
master selects the slave device from which it expects data either by separate select
lines, or by sending a special command to this slave. The selected slave then switches
its MRST line to output, until it gets a deselection signal or command.
The receive line needs an external pullup in this case. Corruption of the data on the
receive line sent by the selected slave is avoided, when all slaves which are not
selected for transmission to the master only send ’ones’. Since this high level is not
actively driven onto the line, but only held through the pullup device, the selected slave
can pull this line actively to a low level when transmitting a zero bit. The master selects
the slave device, from which it expects data either by separate select lines, or by
sending a special command to this slave.
Master
Shift Register
SSC Full Duplex Configuration
Clock
Device
MTSR
CLK
MRST
1
Receive
Clock
Transmit
120
Device
Device
MTSR
MTSR
CLK
CLK
MRST
MRST
2
2
Multi Function Port (MFP)
Clock
Clock
Shift Register
Shift Register
PEB 20534
PEF 20534
MCS01963
2000-05-30
Slave
Slave