User’s Manual U11969EJ3V0UM00
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CHAPTER 2 PIN FUNCTIONS
(9) P90 to P96 (Port 9) ... 3-state I/O
These pins constitute a 7-bit I/O port, port 9, and are also used to output control signals.
P90 to P96 function not only as I/O port pins but also as control signal output pins and bus hold control signal
output pins in the control mode (external expansion mode) when an external memory is used.
If port 9 is accessed in 8-bit units, the higher 1-bit is ignored if the access is write, and undefined if the access
is read.
Operation mode is specified by the mode specification pin (MODE) and memory expansion mode register
(MM).
(a) Port mode
P90 to P96 can be set in the input or output port mode in 1-bit units by using port 9 mode register (PM9).
(b) Control mode (External Expansion Mode)
P90 to P96 can be used to output control signals when so specified by the MODE pin and MM register
when an external memory is used.
(i)
LBEN (Lower Byte Enable) ... output
This is the lower byte enable signal of the 16-bit external data bus.
This signal changes in synchronization with the rising edge of the clock in the T1 state of the bus
cycle. The status of the bus signal remains unchanged in the idle state (TI).
(ii)
UBEN (Upper Byte Enable) ... output
This is the upper byte enable signal of the 16-bit external data bus. It becomes active (low) in byte
access to an odd address. It becomes inactive (high) in byte access to an even address.
This signal changes in synchronization with the rising of the clock in the T1 state of the bus cycle.
The status of the bus signal remains unchanged in the idle state (TI).
Access
UBEN
LBEN
A0
Word Access
0
0
0
Half-word Access
0
0
0
Byte Access
Even address
1
0
0
Odd address
0
1
1
(iii)
R/W (Read/Write Status) ... output
This is a status signal output pin that indicates whether the bus cycle for external access is a read
or write cycle. It goes high in the read cycle and low in the write cycle.
This signal changes in synchronization with the rising edge of the clock in the T1 state of the bus
cycle. It goes high in the idle state (TI).
(iv)
DSTB (Data Strobe) ... output
This is the access strobe signal of the external data bus.
It becomes active (low) in the T2 or TW state of the bus cycle, and becomes inactive (high) in the
idle state (TI).
(v)
ASTB (Address Strobe) ... output
This is the latch strobe signal of the external address bus.
It becomes active (low) in synchronization with the falling edge of the clock in the T1 state of the
bus cycle, and becomes inactive (high) in synchronization with the falling edge of the clock in the
T3 state. It goes high in the idle state (TI).
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