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CHAPTER 3 FUNCTIONAL DESCRIPTION
User’s Manual S14054EJ4V0UM
53
(1) Controlling reading/writing registers
To read an internal register of the
µ
PD98431, the host system sets the address of the register to be read in
A[10:0], and makes the RW signal high and the CS# signal low. The
µ
PD98431 recognizes read access by the
host system by checking the statuses of the RW and CS# signals. Then it makes the ACK# signal high once and
reads the necessary data. When the read data is written to D[31:0], the
µ
PD98431 makes the ACK# signal low.
After the ACK# signal has gone low, the host system reads the data in D[31:0], and then returns the CS# signal
to the high level. The host system must keep the statuses of the A[10:0], RW, and CS# signals until the ACK#
signal has gone low and the host system reads the data. When the host system reads data and makes the CS#
signal high, the
µ
PD98431 completes the read cycle. The ACK# signal goes low for the duration of one cycle of
HCLK.
To write data to an internal register of the
µ
PD98431, the host system writes the address of the register to which
data is to be written, to A[10:0], and the write data to D[31:0]. It then makes the RW and CS# signals low. When
the
µ
PD98431 recognizes the write access by the host system by checking the statuses of the RW and CS#
signals, it makes the ACK# signal high once, and starts writing data to D[31:0]. After writing has been
completed, the
µ
PD98431 makes the ACK# signal low to report to the host system. The host system must keep
the statuses of the A[10:0], D[31:0], RW, and CS# signals until the ACK# signal goes low and the host system
has completed writing data. When writing has been completed and the host system makes the CS# signal high,
the
µ
PD98431 completes the write cycle. The ACK# signal goes low for the duration of one cycle of HCLK.
(2) Register address mapping
The registers accessed by the host system are classified as port control registers, statistics counters, and global
registers. A port control register and a statistics counter are provided for each port and are used to read the
setting of the operation, status information, or statistics information of each port. The global register is used to
perform setting related to all the ports and is used for all the ports.
These registers are specified by the address data in A[10:0]. A[10:0] consists of two parts. The port number of
the port whose register is to be accessed is written to the high-order bits, A[10:8], and the address of the register
to be accessed is written to the low-order bits, A[7:0]. Figure 3-12 shows an example of relation between a port
number and a register address for reference.
Figure 3-12. Register Address Bus
A10
A9
A8
A7
A6
A5
A4
A3
A2
A1
A0
Port number
Register address
A10
A9
A8
A7
A6
A5
A4
A3
A2
A1
A0
0
1
1
1
0
0
1
0
0
0
0
Example
: To access MACC3 register (register address: 90H) of port 3
To access the global register, the value of A[10:8] is ignored.
The registers related to the MII management interface (MIIC, MCMD, MADR, MWTD, MRDD, and MIND
registers) are valid only when the port number is set to 0.
Содержание mPD98431
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