CHAPTER 2 PIN FUNCTIONS
User’s Manual U13850EJ4V0UM
65
(ii) UBEN (Upper Byte Enable)
∙∙∙
output
This is an upper byte enable signal output pin for an external 16-bit data bus. During byte access of
even-numbered addresses, these pins are set as inactive (high level). The output changes in
synchronization with the rising edge of the clock in the T1 state of the bus cycle. When the timing sets
the bus cycle as inactive, the previous bus cycle’s address is retained.
Access
UBEN
LBEN
AD0
Word access
0
0
0
Half word access
0
0
0
Byte access
Even-numbered address
1
0
0
Odd-numbered address
0
1
1
(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 or V850/SB2 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 or V850/SB2 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 or V850/SB2 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 lower data in an external 16-bit data bus. Output occurs
during the write cycle, similar to DSTB.