![Renesas mPD98431 User Manual Download Page 54](http://html.mh-extra.com/html/renesas/mpd98431/mpd98431_user-manual_1440626054.webp)
CHAPTER 3 FUNCTIONAL DESCRIPTION
User’s Manual S14054EJ4V0UM
52
Figure 3-11. Timing for Changing FIFO Bus Read/Write in 64-Bit Single Bus Mode (2/2)
(b) Example of timing for changing read cycle to write cycle
FCLK
FEN#
FRW
TXFBA[N]
RXFA
FDQ[3]
FDQ[2]
FDQ[1]
FDQ[0]
RXFPT[2:0]
TXFPT[2:0]
FD[63:0]
PASS
SKIP
Idle
Idle
Start
Middle
Middle
TA
Port N
Port M
XX
XX
Port N
3 byte
ending
n th
word
64 bits
n
−
1 th
word
64 bits
n
−
2 th
word
64 bits
n
−
3 th
word
64 bits
1st word
64 bits
2nd word
64 bits
3rd word
64 bits
4th word
64 bits
(4) Little endian/big endian
The
µ
PD98431 has a function to select little endian or big endian as the byte order of the transmit/receive data
on the FIFO interface. Little endian or big endian is selected by using the BUSMODE bit of the MACC3 register.
In the little endian mode, data is transferred starting from the least significant byte of the data bus. In the big
endian mode, data transfer starts from the most significant byte. The setting of the BUSMODE bit of the MACC3
register does not influence the byte order of the register bus interface.
3.7.2 Register bus interface
The
µ
PD98431 provides a register bus interface via which the internal registers of the
µ
PD98431, such as control
registers and statistics counters, can be accessed. The register bus interface consists of a 32-bit bidirectional data
bus and an 11-bit address bus and control signals (CS#, RW, and ACK# signals).