CHAPTER 2 PIN FUNCTIONS
User’s Manual U12688EJ4V0UM00
56
(iv) IOWR (I/O Write) ··· 3-state output
This is the write strobe signal for external I/O during DMA flyby transfer. It indicates whether the bus
cycle currently being executed is a write cycle for external I/O during flyby transfer, or a write cycle for
the SRAM area.
In order to make it possible to connect directly to memory or external I/O during DMA flyby transfer,
IOWR rises before RD rises.
Furthermore, this external I/O can be accessed even when it is assigned to the SRAM area.
(10) P90 to P97 (Port 9) ··· 3-state I/O
Port 9 is an 8-bit input/output port that can be set to input or output in 1-bit units.
Besides functioning as a port, in the control mode it operates as a control signal output and bus hold control
signal input/output when memory is externally expanded.
The operation mode can be set as port or control in 1-bit units, specified by the port 9 mode control register
(PMC9).
(a) Port mode
P90 to P97 can be set to input or output in bit units by the port 9 mode register (PM9).
(b) Control mode
P90 to P97 can be set in the port/control mode in bit units by the PMC9 register.
(i)
LCAS (Lower Column Address Strobe) ··· 3-state output
This is the strobe signal for column address for DRAM and the strobe signal for the CBR refresh
cycle.
In the data bus, the lower byte is valid.
(ii) UCAS (Upper Column Address Strobe) ··· 3-state output
This is the strobe signal for column address for DRAM and the strobe signal for the CBR refresh
cycle.
In the data bus, the higher byte is valid.
(iii) LWR (Lower Byte Write Strobe) ··· 3-state output
This strobe signal shows whether the bus cycle currently being executed is a write cycle for the
SRAM, external ROM, external peripheral I/O, or page ROM.
In the data bus, the lower byte becomes valid. If the bus cycle is a lower memory write, it becomes
active at the rise of the T1 state’s CLKOUT signal and becomes inactive at the rise of the T2 state’s
CLKOUT signal.
(iv) UWR (Upper Byte Write Strobe) ··· 3-state output
This strobe signal shows whether the bus cycle currently being executed is a write cycle for the
SRAM, external ROM, external peripheral I/O, or page ROM.
In the data bus, the higher byte becomes valid. If the bus cycle is a higher memory write, it becomes
active at the rise of the T1 state’s CLKOUT signal and becomes inactive at the rise of the T2 state’s
CLKOUT signal.
Summary of Contents for V850E/MS1 UPD703100
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