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CHAPTER 2 PIN FUNCTIONS
39
2.3.3 Control Memory Interface Signals
The control memory interface is used by the
μ
PD98405 to enable access to the external control memory and
external PHY layer device. The interface consists of non-multiplexed 19-bit address and 32-bit data buses.
The host can access control memory only via this interface.
Symbol
Pin No.
I/O
I/O level
Function
CD31-CD0
119 - 123,
126 - 130,
132 - 136,
139 - 144,
146 - 150,
155 - 159, 161
I/O
3-state
TTL
Control Memory Data
The CD31 to CD0 bus is a 32-bit, bi-directional, 3-state
data bus used to transfer data to and from the control
memory or the PHY layer device.
These pins are connected to internal pull-down
resistors.
CPAR3-
CPAR0
162 - 165
I/O
TTL
Control Memory Parity
The CPAR3 to CPAR0 signals indicate the parity on
each octet of the CD31 to CD0 bus. The
μ
PD98405
checks parity during read cycles (if enabled) and
generates parity during write cycle.
These pins are connected to internal pull-down
resistors.
CA18-CA0
166,
168 - 173,
176 - 181,
183 - 188
O
TTL
Control Memory Address
The 19-bit CA18 to CA0 bus specifies the address of
the control memory or PHY layer device for a read or
write operation.
CWE_B
195
O
TTL
Control Memory Write Enable
The CWE_B signal determines the direction of control
memory access.
1:
Read access
0:
Write access
COE_B
196
O
TTL
Control Memory Output Enable
The COE_B signal enables/disables the control memory
data output lines.
CBE3_B-
CBE0_B
191 - 194
O
TTL
Local Port Byte Enable
The CBE3_B to CBE0_B signals determine which byte
or bytes out of the four on the control port is to be
written in write cycle, and which of the bytes is read in
read cycle.
INITD
197
I
TTL
Initialization Disable
The INITD signal is used to disable automatic
initialization of the control memory when testing the
chip. INITD must be directly connected to GND in
normal operation other than testing.