Motorola MC68306 User Manual page 42

STATE 12 The write portion of the cycle starts in S12. The valid function codes on
FC2–FC0, the address bus lines, AS, and R/W remain unaltered.
STATE 13 During S13, no bus signals are altered.
STATE 14 On the rising edge of S14, the processor drives R/W low.
STATE 15 During S15, the data bus is driven out of the high-impedance state as the
data to be written are placed on the bus.
STATE 16 At the rising edge of S16, the processor asserts UDS /LDS . The processor
waits for D T A C K or BERR . If neither termination signal is asserted
before the falling edge at the close of S16, the processor inserts wait states
(full clock cycles) until either DTACK or BERR is asserted.
Case W1: DTACK with or without BERR .
STATE 17 During S17, no bus signals are altered.
STATE 18 During S18, no bus signals are altered.
STATE 19 On the falling edge of the clock entering S19, the processor negates AS and
UDS /LDS . As the clock rises at the end of S19, the processor
places the data bus in the high-impedance state, and drives
R/W high. The device negates DTACK or BERR at this time.
Case R2: DTACK and BERR on read.
STATE 5 During S5, no bus signals are altered.
STATE 6 During S6, no bus signals are altered, and data from the device is ignored.
STATE 7 AS and U D S /LDS are negated. The cycle terminates without the write
portion.
Case R3: BERR only on read.
STATE 5 During S5, no bus signals are altered.
STATE 6 During S6, no bus signals are altered..
STATE 7 During S7, no bus signals are altered.
STATE 8 During S8, no bus signals are altered.
STATE 9 AS and U D S /LDS are negated. The cycle terminates without the write
portion.
Case W2: BERR only on write.
3-10 MC68306 USER'S MANUAL MOTOROLA