Motorola MC68VZ328 - Manual (Page 172)

10-2 MC68VZ328 User’s Manual
Status of I/O Ports During Reset
10.2 Status of I/O Ports During Reset
Two types of resets affect the states of the MC68VZ328’s I/O ports: warm reset and power-up reset. A
warm reset refers to any reset initiated while power to the processor remains uninterrupted. A power-up
reset occurs the first time power is supplied to the MC68VZ328. Power-up resets are also called cold start
resets.
10.2.1 Warm Reset
Figure 10-1 on page 10-3 details timing during a warm reset. All I/O ports, except Ports B and M, reset to
their default states on assertion of the reset signal and remain at their default states during the time period
labeled Reset Assertion Time Length. The port default state is determined by the register reset values of
the I/O port registers. Register reset values are found in Table 3-1 on page 3-2 and Table 3-2 on page 3-8.
Ports B and M maintain their previous programmed states on reset assertion and retain their states during
the Reset Assertion Time Length. The previous states of Ports B and M before reset assertion are, for the
purposes of the figure, assumed.
Table 10-1. Dedicated I/O Functions of Ports
Port Dedicated I/O Module Dedicated I/O Module Dedicated I/O Module Dedicated I/O Module
A Lower byte of data bus
B Chip-select DRAM controller GP timers PWM output
C LCD controller
D Interrupt controller
E SPI DRAM controller UART Bus control
F DRAM controller CGM Address bits 23–20 Interrupt request 5
LCD contrast Chip-select
G Bus control In-circuit emulation Address bit 0
J UART SPI
K Bus control LCD controller SPI
M DRAM controller