
156
6.9
Resets and the Bus Controller
In a power-on reset, the H8S/2214, including the bus controller, enters the reset state at that point,
and an executing bus cycle is discontinued.
In a manual reset, the bus controller’s registers and internal state are maintained, and an executing
external bus cycle is completed. In this case,
WAIT input is ignored and write data is not
guaranteed.
6.10
External Module Expansion Function
6.10.1
Overview
The H8S/2214 has an external module expansion function to provide for the addition of peripheral
devices. Using this function to provide a combination of H8S/2214 and external modules makes it
possible to implement a multichip system on the user board.
Figure 6-21 shows a block diagram.
Bus access states can be changed by means of a bus controller setting.
The
EXMS signal is output to external modules for addresses H'FFFF40 to H'FFFF5F.
Priority and DTC activation can be specified for interrupts
EXIRQ7 to EXIRQ0 in the same way
as for the H8S/2214’s on-chip supporting functions.
The DTC data transfer end signal for
EXIRQ7 to EXIRQ0 interrupt input is output from
EXDTCE. Also, the inverse of the value of bit 0 in module stop control register B is output from
EXMSTP.
A23 to A0
D15 to D0
EXMSTP
EXMS
EXDTCE
EXIRQ7 to EXIRQ0
H8S/2214
External module
Figure 6-21 Multichip Block Diagram