m38039mf-xxxsp Mitsumi Electronics, Corp., m38039mf-xxxsp Datasheet - Page 58

• Manufacturer Part Number: m38039mf-xxxsp
• Description: Single-chip 8-bit Cmos Microcomputer
• Manufacturer: Mitsumi Electronics, Corp.

Serial I/O3
Serial I/O3 can be used as either clock synchronous or asynchro-
nous (UART) serial I/O. A dedicated timer is also provided for
baud rate generation.
Fig. 48 Block diagram of clock synchronous serial I/O3
Fig. 49 Operation of clock synchronous serial I/O3
58
b u f f e r r e g i s t e r ( a d d r e s s 0 0 3 0
W r i t e p u l s e t o r e c e i v e / t r a n s m i t
R e c e i v e e n a b l e s i g n a l S
( 1 / 2 t o 1 / 2 0 4 8 o f t h e i n t e r n a l
c l o c k , o r a n e x t e r n a l c l o c k )
Notes 1 : A s t h e t r a n s m i t i n t e r r u p t ( T I ) , w h i c h c a n b e s e l e c t e d , e i t h e r w h e n t h e t r a n s m i t b u f f e r h a s e m p t i e d ( T B E = 1 ) o r a f t e r t h e
(f(X
P3
P 3
P3
P3
CIN
6
7
4
5
/S
/ S
T r a n s f e r s h i f t c l o c k
/R
/T
S e r i a l o u t p u t T x D
2 : I f d a t a i s w r i t t e n t o t h e t r a n s m i t b u f f e r r e g i s t e r w h e n T S C = 0 , t h e t r a n s m i t c l o c k i s g e n e r a t e d c o n t i n u o u s l y a n d s e r i a l d a t a
3 : T h e r e c e i v e i n t e r r u p t ( R I ) i s s e t w h e n t h e r e c e i v e b u f f e r f u l l f l a g ( R B F ) b e c o m e s “ 1 ” .
f(X
) in low-speed mode)
S e r i a l i n p u t R x D
RDY3
C L K 3
X
X
t r a n s m i t s h i f t o p e r a t i o n h a s e n d e d ( T S C = 1 ) , b y s e t t i n g t h e t r a n s m i t i n t e r r u p t s o u r c e s e l e c t i o n b i t ( T I C ) o f t h e s e r i a l I / O 3
c o n t r o l r e g i s t e r .
i s o u t p u t c o n t i n u o u s l y f r o m t h e T x D p i n .
IN
D
D
)
3
3
B R G c o u n t s o u r c e s e l e c t i o n b i t
R D Y 3
1 6
F/F
3
3
)
T B E = 0
1 / 4
F a l l i n g - e d g e d e t e c t o r
TBE = 1
TSC = 0
D
D
0
0
Receive buffer register 3
R e c e i v e s h i f t r e g i s t e r 3
Transmit buffer register 3
T r a n s m i t s h i f t r e g i s t e r 3
D
D
D a t a b u s
Data bus
1
1
Address 0030
Shift clock
Serial I/O3 synchronous
clock selection bit
Frequency division ratio 1/(n+1)
Baud rate generator 3
Address 0030
D
D
Shift clock
Address 002F
2
2
(1) Clock Synchronous Serial I/O Mode
Clock synchronous serial I/O3 mode can be selected by setting
the serial I/O3 mode selection bit of the serial I/O3 control register
(bit 6 of address 0032
For clock synchronous serial I/O, the transmitter and the receiver
must use the same clock. If an internal clock is used, transfer is
started by a write signal to the transmit/receive buffer register.
16
D
D
3
3
Clock control circuit
16
C l o c k c o n t r o l c i r c u i t
16
SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER
Serial I/O3 control register
Transmit interrupt source selection bit
Serial I/O3 status register
Receive buffer full flag (RBF)
D
D
1/4
4
4
MITSUBISHI MICROCOMPUTERS
16
) to “1”.
D
D
Receive interrupt request (RI)
5
5
3803/3804 Group
Transmit buffer empty flag (TBE)
Transmit shift completion flag (TSC)
Transmit interrupt request (TI)
D
D
6
6
A d d r e s s 0 0 3 2
O v e r r u n e r r o r ( O E )
d e t e c t i o n
Address 0031
R B F = 1
T S C = 1
D
D
7
7
1 6
16