Chapter 15: Serial Port Interface
TX7901 User’s Manual (Rev. 6.30T – Nov, 2001)
15-10
0, the shift clock will idle Low. When CPOL equals 1, it will idle High.
In the Master Mode, when a transfer is initiated by writing a new value to the SEDR register,
the new data are placed on the MOSI signal for half a clock cycle before the shift clock
starts to operate. The BOS flag determines whether the value will be shifted out in an MSB
or LSB order. After the last shift cycle, the SEF flag (in Compatibility Mode) or the TSRC flag
and TSTC flags (in Toshiba Mode) will be asserted.
In the Slave Mode, the SEDR register is not allowed to be written to when the SS_n signal is
low. A write attempt in this state will result in a write collision and the WCOL bit will be
asserted in the SESR register. Therefore, even if the transfer has been completed and the
SEF or TSRC bit has been asserted, the software has to wait until the SS signal goes High
again before writing a new value to SEDR. To allow the use of a MicroDMA to transfer
values to the SEDR register in the Slave Mode, the TSTC signal is delayed until SS_n goes
High.
15.6.2 CPHA EQUALS 1 FORMAT
Figure 15-4 shows the transfer format for a CPHA=1 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 15-4 CPHA Equals 1 Transfer Format
In this transfer format, the first bit is shifted in on the second clock edge. This will be on a
falling edge when CPOL equals 0 and on a rising edge when CPOL equals 1. If CPOL
equals 0, the shift clock will idle low. When CPOL equals 1, it will idle high.
In the Master Mode, when a transfer is initiated by writing a new value to the SEDR register,
the new data are placed on the MOSI signal with the first edge of the shift clock. Again, the
first bit to be transferred will be determined by the BOS bit in the SECR register.
Unlike the CPHA equals 0 format, SEDR is allowed to be written to in the Slave Mode even
if the SS_n signal is low.
In both the Master Mode and the Slave Mode, the SEF flag (in the Compatibility Mode) or
the TSRC and TSTC flags (in the Toshiba Mode) will be asserted simultaneously after the
last shift cycle completes. Any attempt to write to this register while the data shifting is still in
progress will result in a write collision.
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: ......
Page 259: ...Chapter 13 Removed TX7901 User s Manual Rev 6 30T Nov 2001 13 1 13 Removed ...
Page 260: ...Chapter 13 Removed TX7901 User s Manual Rev 6 30T Nov 2001 13 2 ...