4518 Datasheet, PDF (53/160 Pages) Renesas Technology Corp – SINGLE-CHIP 4-BIT CMOS MICROCOMPUTER

4518 Group
SERIAL INTERFACE
The 4518 Group has a built-in clock synchronous serial I/O which
can serially transmit or receive 8-bit data.
Serial I/O consists of;
• serial I/O register SI
• serial I/O control register J1
• serial I/O transmit/receive completion flag (SIOF)
• serial I/O counter
Registers A and B are used to perform data transfer with internal
CPU, and the serial I/O pins are used for external data transfer.
The pin functions of the serial I/O pins can be set with the register
J1.
Table 14 Serial I/O pins
Pin
P20/SCK
P21/SOUT
P22/SIN
Pin function when selecting serial I/O
Clock I/O (SCK)
Serial data output (SOUT)
Serial data input (SIN)
Note: Even when the SCK, SOUT, SIN pin functions are used, the input of
P20, P21, P22 are valid.
1/8
1/4
INSTCK
1/2
P20/SCK ^SCK
P21/SOUT ^SOUT
J13J12
00
01
10
11
Synchronous
circuit
Serial I/O counter (3)
QS
R
SIN
P22/SIN
J11 J10
MSB Serial I/O register (8) LSB
TABSI
TSIAB
TABSI
Register B (4) Register A (4)
SIOF
Serial I/O
interrupt
SST
instruction
Internal reset signal
Fig. 42 Serial I/O structure
Table 15 Serial I/O control register
Serial I/O control register J1
at reset : 00002
at RAM back-up : state retained
J13 J12
J13
00
Serial I/O synchronous clock selection bits 0 1
J12
10
11
J11
Serial I/O port function selection bits
J10
J11 J10
00
01
10
11
Note: “R” represents read enabled, and “W” represents write enabled.
Synchronous clock
Instruction clock (INSTCK) divided by 8
Instruction clock (INSTCK) divided by 4
Instruction clock (INSTCK) divided by 2
External clock (SCK input)
Port function
P20, P21,P22 selected/SCK, SOUT, SIN not selected
SCK, SOUT, P22 selected/P20, P21, SIN not selected
SCK, P21, SIN selected/P20, SOUT, P22 not selected
SCK, SOUT, SIN selected/P20, P21,P22 not selected
R/W
TAJ1/TJ1A
Rev.3.01 2005.06.15 page 53 of 157
REJ03B0008-0301