Chapter 15: Serial Port Interface
TX7901 User’s Manual (Rev. 6.30T – Nov, 2001)
15-9
15.5.2 SDMISO
and
SDMOSI
The SDMISO and SDMOSI data pins are used for transmitting and receiving serial data.
When the TSEI is configured as a master, SDMISO is the data input line, and SDMOSI is
the master data output line. When the TSEI is configured as a slave, these pins reverse
roles. In a multiple master system, all SCLK pins are tied together, all SDMOSI pins are tied
together, and all SDMISO pins are tied together. A single TSEI device is configured as a
master and all other TSEI devices on the TSEI bus are configured as slaves. The single
master drives data out from its SCLK and SDMOSI pins to the SCLK and SDMOSI pins of
the slaves. One selected slave device optionally drives data out from its SDMISO pin to the
SDMISO master pin.
15.5.3 SS_N
The SS_n pin behaves differently on master and slave devices. On a slave device, this pin
enables the TSEI slave for a transfer. If the SS_n pin of a slave is inactive (high), the device
ignores TSCLK clocks and keeps the SDMISO output pin in the high-impedance state. On a
master device, the SS_n pin serves as an error-detection input for the TSEI. If the SS_n pin
goes low while the TSEI is a master, it indicates that some other device on the TSEI bus is
attempting to be a master. This attempt causes the master device sensing the error to
immediately exit the TSEI bus to avoid potentially damaging driver contentions. Such error
detection is called “mode fault.”
15.6 TSEI Transfer Formats
The CPHA and CPOL registers in the SECR register set the transfer format. CPHA switches
between fundamentally different transfer protocols.
15.6.1 CPHA Equals 0 Format
Figure 15-3 shows the transfer format for a CPHA=0 transfer.
1
2
3
4
5
6
7
8
Cycle #
SCK (CPOL=0)
SCK (CPOL=1)
MOSI
MISO
SEF
(Compatibility
Mode)
TSRC
(Toshiba Mode)
TSTC
(Toshiba Mode)
SS
Master
Mode
Slave
Mode
Figure 15-3 CPHA Equals 0 Transfer Format
In this transfer format, the first bit is shifted in on the first clock edge. This will be on a rising
edge when CPOL equals 0 and on a falling edge when CPOL equals 1. When CPOL equals
Summary of Contents for TMPR7901
Page 1: ...TX System RISC TX79 Family TMPR7901 Symmetric 2 way superscalar 64 bit CPU ...
Page 14: ...Handling Precautions ...
Page 15: ......
Page 17: ...1 Using Toshiba Semiconductors Safely 1 2 ...
Page 41: ...4 Precautions and Usage Considerations 4 2 ...
Page 42: ...TX7901 User s Manual Rev 6 30T November 2001 DOCUMENT NUMBER M 99 00004 07 ...
Page 43: ......
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Page 260: ...Chapter 13 Removed TX7901 User s Manual Rev 6 30T Nov 2001 13 2 ...