Typewriter User Manual

MOTOROLA MC68340 USER’S MANUAL 7- 39
TxCTS—Transmitter Clear-to-Send
1 = Enables clear-to-send operation. The transmitter checks the state of the
CTS≈
input each time it is ready to send a character. If CTS≈ is asserted, the character
is transmitted. If
CTS≈ is negated, the channel TxDx remains in the high state,
and the transmission is delayed until
CTS≈ is asserted. Changes in CTS≈ while
a character is being transmitted do not affect transmission of that character. If
both TxCTS and TxRTS are enabled, TxCTS controls the operation of the
transmitter.
0 = The
CTS≈ has no effect on the transmitter.
SB3–SB0—Stop-Bit Length Control
These bits select the length of the stop bit appended to the transmitted character as
listed in Table 7-10. Stop-bit lengths of nine-sixteenth to two bits, in increments of one-
sixteenth bit, are programmable for character lengths of six, seven, and eight bits. For a
character length of five bits, one and one-sixteenth to two bits are programmable in
increments of one-sixteenth bit. In all cases, the receiver only checks for a high
condition at the center of the first stop-bit position—i.e., one bit time after the last data
bit or after the parity bit, if parity is enabled.
If an external 1× clock is used for the transmitter, MR2 bit 3 = 0 selects one stop bit, and
MR2 bit 3 = 1 selects two stop bits for transmission.
Table 7-10. SBx Control Bits
SB3 SB2 SB1 SB0 Length 6-8 Bits Length 5 Bits
0 0 0 0 0.563 1.063
0 0 0 1 0.625 1.125
0 0 1 0 0.688 1.188
0 0 1 1 0.750 1.250
0 1 0 0 0.813 1.313
0 1 0 1 0.875 1.375
0 1 1 0 0.938 1.438
0 1 1 1 1.000 1.500
1 0 0 0 1.563 1.563
1 0 0 1 1.625 1.625
1 0 1 0 1.688 1.688
1 0 1 1 1.750 1.750
1 1 0 0 1.813 1.813
1 1 0 1 1.875 1.875
1 1 1 0 1.938 1.938
1 1 1 1 2.000 2.000
Frees
cale Semiconductor,
I
Freescale Semiconductor, Inc.
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