
CHAPTER 2 PIN FUNCTIONS
48
(iii) R/W (Read/Write Status) ··· output
This is an output pin for the status signal pin that indicates whether the bus cycle is a read cycle or write
cycle during external access. High level is set during the read cycle and low level is set during the write
cycle. The output changes in synchronization with the rising edge of the clock in the T1 state of the bus
cycle. High level is set when the timing sets the bus cycle as inactive.
(iv) DSTB (Data Strobe) ··· output
This is an output pin for the external data bus’s access strobe signal. Output becomes active (low level)
during the T2 and TW states of the bus cycle. Output becomes inactive (high level) when the timing
sets the bus cycle as inactive.
(v)
ASTB (Address Strobe) ··· output
This is an output pin for the external address bus’s latch strobe signal. Output becomes active (low
level) in synchronization with the falling edge of the clock during the T1 state of the bus cycle, and
becomes inactive (high level) in synchronization with the falling edge of the clock during the T3 state of
the bus cycle. Output becomes inactive when the timing sets the bus cycle as inactive.
(vi) HLDAK (Hold Acknowledge) ··· output
This is an output pin for the acknowledge signal that indicates high impedance status for the address
bus, data bus, and control bus when the V850/SB1 receives a bus hold request.
The address bus, data bus, and control bus are set to high impedance status when this signal is active.
(vii) HLDRQ (Hold Request) ··· input
This is an input pin by which an external device requests the V850/SB1 to release the address bus,
data bus, and control bus. This pin accepts asynchronous input for CLKOUT. When this pin is active,
the address bus, data bus, and control bus are set to high impedance status. This occurs either when
the V850/SB1 completes execution of the current bus cycle or immediately if no bus cycle is being
executed, then the HLDAK signal is set as active and the bus is released.
(viii)WRL (Write Strobe Low Level Data) ··· output
This is a write strobe signal output pin for the low-order data in an external 16-bit data bus. Output
occurs during the write cycle, similar to DSTB.