MITSUBISHI MICROCOMPUTERS
38B5 Group
SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER
30
PRELIMINARY
Notice: This s not a final specification.
Some parametric imits are subject to change.
When the internal synchronous clock is selected, in the 8-bit serial
I/O mode and the automatic transfer serial I/O mode (S
BUSY1
out-
put function outputs in 1-byte units), the S
BUSY1
output goes to “L”
and the S
BUSY1
output goes to “H” before 0.5 cycle (transfer clock)
of the timing at which the transfer clock from the S
CLK1
output goes
to “L” at a start of transmit/receive operation.
In the automatic transfer serial I/O mode (the S
BUSY1
output func-
BUSY1
output goes to “L” and the
_________
S
BUSY1
output goes to “H” when the first transmit data is written into
the serial I/O1 register (address 001B
16
).
When the external synchronous clock is selected, the S
BUSY1
out-
put goes to “L” and the S
BUSY1
output goes to “H” when transmit
data is written into the serial I/O1 register to start a transmit opera-
tion, regardless of the serial I/O transfer mode.
At termination of transmit/receive operation, the S
BUSY1
output re-
turns to “H” and the S
BUSY1
output returns to “L”, the initial status,
when the serial transfer status flag is set to "0", regardless of whether
the internal or external synchronous clock is selected.
Furthermore, in the automatic transfer serial I/O mode (S
BUSY1
out-
put function outputs in 1-byte units), the S
BUSY1
output goes to “H”
and the S
BUSY1
output goes to “L” each time 1-byte of receive data
is written into the automatic transfer RAM.
Fig. 27 S
BUSY1
Output Operation
(internal synchronous clock, 8-bits serial I/O)
Fig. 28 S
BUSY1
Output Operation
(external synchronous clock, 8-bits serial I/O)
Fig. 29 S
BUSY1
Output Operation in Automatic Transfer Serial I/O Mode
(internal synchronous clock, S
BUSY1
output function outputs each 1-byte)
S
BUSY1
S
CLK1
S
OUT1
Serial transfer
status flag
Serial transfer
status flag
S
BUSY1
S
CLK1
Write to Serial
I/O1 register
S
CLK1
S
BUSY1
S
OUT1
Automatic transfer
interval
Serial transfer
status flag
Automatic transfer RAM
→
Serial I/O1 register
Serial I/O1 register
→
Automatic transfer RAM