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CHAPTER 2 PIN FUNCTIONS
(iii) R/W (Read/Write Status) ... output
This is a status signal 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).
(vi) HLDAK (Hold Acknowledge) ... output
This is an acknowledge signal output pin that indicates that the V853 has set the address bus, data
bus, and control bus in the high-impedance state in response to a bus hold request.
As long as this signal is active, the address bus, data bus, and control bus remain in a high impedance
state.
(vii) HLDRQ (Hold Request) ... input
This input pin is used by an external device to request that the V853 relinquish control of the address
bus, data bus, and control bus. This pin can be input asynchronously with CLKOUT. When this signal
becomes active, the V853 sets the address bus, data bus, and control bus in the high-impedance
state, after the current bus cycle completes. If there is no current bus activity, the address bus, data
bus, and control bus are immediately set to high-impedance. HLDAK is then made active and the
bus and control lines are released.
(10) P110 to P117 (Port 11) ... 3-state I/O
Port 10 is an 8-bit I/O port that can be set in the input or output mode in 1-bit units. In addition to the function
as a port, the pins constituting port 10 are used as input/output of RPU and external interrupt request.
(a) Port mode
P110 to P117 can be set in the input or output mode, in 1-bit units, by the port mode register (PM11).
(b) Control mode
P110 to P117 can be set in the port or control mode, in 1-bit units, by port 11 mode control register
(PMC11).
(i)
TO140, TO141 (Timer Output) ... output
These pins output pulse signals from timer 1.
(ii)
TCLR14 (Timer Clear) ... input
This pin inputs an external clear signal to timer 1.