User’s Manual U12688EJ4V0UM00
103
CHAPTER 4 BUS CONTROL FUNCTION
The V850E/MS1 is provided with an external bus interface function by which external memories such as ROM and
RAM, and I/O can be connected.
4.1
Features
•
16-bit/8-bit data bus sizing function
•
8-space chip select output function
•
Wait function
•
Programmable wait function, capable of inserting up to 7 wait states for each memory block
•
External wait function via WAIT pin
•
Idle state insertion function
•
Bus mastership arbitration function
•
Bus hold function
•
Capable of connecting to external devices via alternate function pins
4.2
Bus Control Pins
The following pins are used for connecting to external devices:
Bus Control Pin (Function When in the Control Mode)
Function When in the Port
Mode
Register Which Performs
Port/Control Mode Switching
Data bus (D0 to D7)
P40 to P47 (Port 4)
MM
Data bus (D8 to D15)
P50 to P57 (Port 5)
MM
Address bus (A0 to A7)
PA0 to PA7 (Port A)
MM
Address bus (A8 to A15)
PB0 to PB7 (Port B)
MM
Address bus (A16 to A23)
P60 to P67 (Port 6)
MM
Chip select (CS0 to CS7, RAS0 to RAS7, IORD, IOWR)
P80 to P87 (Port 8)
PMC8
Read/write control (LCAS, UCAS, LWR, UWR, RD, WE, OE)
P90 to P93, P95 (Port 9)
PMC9
Bus cycle start (BCYST)
P94 (Port 9)
PMC9
External wait control (WAIT)
PX6 (Port X)
PMCX
Bus hold control (HLDAK, HLDRQ)
P96, P97 (Port 9)
PMC9
DRAM refresh control (REFRQ)
PX5 (Port X)
PMCX
Internal system clock (CLKOUT)
PX7 (Port X)
PMCX
Remark
In the case of single-chip mode 1 and ROM-less modes 0 and 1, when the system is reset, each bus
control pin becomes unconditionally valid (however, D8 to D15 are valid only in single-chip mode 1 and
ROM-less mode 0). For details, refer to 3.4.6 External expansion mode.
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