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User’s Manual U14492EJ3V0UD
CHAPTER 4 BUS CONTROL FUNCTION
The V850E/IA1 is provided with an external bus interface function by which external I/O and memories, such as
ROM and RAM, can be connected.
4.1
Features
• 16-bit/8-bit data bus sizing function
• 8-space chip select function
• Wait function
• Programmable wait function, through which up to 7 wait states can be inserted for each memory block
• External wait function via WAIT pin
• Idle state insertion function
• Bus hold function
• External device connection enabled via bus control/port alternate function pins
4.2
Bus Control Pins
The following pins are used for connection to external devices.
Bus Control Pin (Function When in Control Mode)
Function When in Port Mode
Register for Port/Control
Mode Switching
Address/data bus (AD0 to AD15)
PDL0 to PDL15 (Port DL)
PMCDL
Address bus (A16 to A23)
PDH0 to PDH7 (Port DH)
PMCDH
Chip select (CS0 to CS7)
PCS0 to PCS7 (Port CS)
PMCCS
Read/write control (LWR/UWR, RD, ASTB)
PCT0, PCT1, PCT4, PCT6
(Port CT)
PMCCT
External wait control (WAIT)
PCM0 (Port CM)
Internal system clock (CLKOUT)
PCM1 (Port CM)
Bus hold control (HLDRQ, HLDAK)
PCM2, PCM3 (Port CM)
PMCCM
Remark
In the case of single-chip mode 1 and ROMless modes 0 and 1, when the system is reset, each bus
control pin becomes unconditionally valid.
4.2.1 Pin status during internal ROM, internal RAM, and on-chip peripheral I/O access
When the internal ROM and RAM are accessed, both the address bus and address/data bus become undefined.
The external bus control signal becomes inactive.
When on-chip peripheral I/O are accessed, both the address bus and address/data bus output the addresses of the
on-chip peripheral I/O currently being accessed. No data is output. The external bus control signal becomes inactive.
Содержание V850E/IA1 mPD703116
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