SERIAL I/O
7902 Group User’s Manual
12-19
12.2.10 CTS/RTS function
When the CTS function is selected, the signal input to the CTSi pin must be at “L” level. (This is one of
the transmit conditions.)
When the RTS function is selected, the RTSi pin outputs the following signals:
(1)
Clock synchronous serial I/O mode
When the receive enable bit (bit 2 at addresses 3516, 3D16) = “0” (reception disabled), the RTSi pin
outputs “H” level.
When the receive enable bit = “0” (reception disabled), the RTSi pin outputs “L” level by setting the
receive enable bit to “1,” or by reading the low-order byte of the UARTi receive buffer register.
When the receive enable bit = “1” (continuously reception), the RTSi pin outputs “L” level by reading
the low-order byte of the UARTi receive buffer register.
When reception has started, the RTSi pin outputs “H” level.
When an internal clock is selected (bit 3 at addresses 3016, 3816 = “0”), do not select the RTS function
because the RTS output is undefined.
(2)
UART mode
When the receive enable bit (bit 2 at addresses 3516, 3D16) = “0” (reception disabled), the RTSi pin
outputs “H” level.
When the receive enable bit = “0” (reception disabled), the RTSi pin outputs “L” level by setting the
receive enable bit to “1,” or by reading the low-order byte of the UARTi receive buffer register.
When the receive enable bit = “1” (continuously reception), the RTSi pin outputs “L” level by reading
the low-order byte of the UARTi receive buffer register.
When reception has started, the RTSi pin outputs “H” level.
Selection of the CTS/RTS function depends on the following bits.
CTS/RTS function select bit (bit 2 at addresses 3416, 3C16: see Figure 12.2.3.)
CTS/RTS enable bit (bit 4 at addresses 3416, 3C16: see Figure 12.2.3.)
CTS0/RTS0 separate select bit (bit 0 at address AC16: see Figure 12.2.13.)
CTS1/RTS1 separate select bit (bit 1 at address AC16: see Figure 12.2.13.)
Table 12.2.1 lists the selection of the CTS/RTS function.
12.2 Block description
!: It may be either “0” or “1.”
Notes 1: When using the CTS0/RTS0 pin, be sure that the D-A2 output enable bit (bit 2 at address 9616) =
“0” (output disabled).
2: When using the P81 or P85 pin as the CTS pin, be sure to clear the corresponding bit of the port
P8 direction register to “0.”
3: When CTSi/RTSi separation is selected, the CLKi pin cannot be used. Accordingly, CTSi/RTSi
cannot be separated in the clock synchronous serial I/O mode. When separating CTSi/RTSi in
UART mode, be sure to select an internal clock.
Table 12.2.1 Selection of CTS/RTS function
0
1
!
0
1
!
CTS/RTS
enable bit
Functions
0
1
CTSi/RTSi
separate select bit
CTS/RTS
function select bit P80/CTS0/RTS0 pin (Note 1)
CTS0
RTS0
P80
P81 or CLK0
CTS0 (Notes 2, 3)
P81 or CLK0
P81/CTS0/CLK0 pin P84/CTS1/RTS1 pin
CTS1
RTS1
P84
P85 or CLK1
CTS1 (Notes 2, 3)
P85 or CLK1
P85/CTS1/CLK1 pin