UPD75518 NEC, UPD75518 Datasheet - Page 95

• Manufacturer Part Number: UPD75518
• Description: 4 BIT SINGLE-CHIP MICROCOMPUTER
• Manufacturer: NEC

Bus release signal
(REL)
Command signal
(CMD)
Acknowledge
signal
(ACK)
Busy signal
(BUSY)
Ready signal
(READY)
Signal name
Master
Master
Master/
slave
Slave
Slave
Output
device
Rising edge of SB0
(SB1) when SCK0 = 1
Falling edge of SB0
(SB1) when SCK0 = 1
Low level signal
output on SB0 (SB1)
during one SCK0 clock
cycle after serial
reception is completed
Low level signal
output on SB0 (SB1)
after acknowledge
signal
High level signal
output on SB0 (SB1)
before serial transfer
is started or after
serial transfer is
completed
Definition
SB0 (SB1)
SB0 (SB1)
SCK0
SB0
(SB1)
SB0
(SB1)
Table 4-10 Various Signals (1/2)
SCK0
SCK0
D0
D0
9
ACK
Timing chart
“H”
“H”
ACK
BUSY
BUSY
READY
READY
• RELT is set.
• CMDT is set.
• BSYE = 1
1
# ACKE = 1
1
$ ACKT is set.
2
# BSYE = 0
$ Execution of
2
Condition for
output
instruction to
write data to
SIO0 (Transfer
start request)
• RELD is set.
• CMDD is clear-
• CMDD is set.
• ACKD is set.
ed.
Flag
operation
–
–
Indicates that CMD
signal follows and
data transmitted is
address data.
(1) Data transmitted
(2) Data transmitted,
Indicates completion
of reception.
Indicates that serial
transfer is disabled
because processing
is in progress.
Indicates that serial
transfar is enabled.
after REL signal
output is address.
with REL signal
not being output,
is command.
Meaning
of signal