Z8F1680SH020SG Datasheet, PDF (326/412 Pages) Zilog, Inc. – High-Performance 8-Bit Microcontrollers

Z8 Encore! XP^® F1680 Series
Product Specification
301
23.2.6. Automatic Reset
The Z8 Encore! XP F1680 Series devices have the capability to switch clock sources dur-
ing operation. If the Autobaud is set and the clock source is switched, the Autobaud value
becomes invalid. A new Autobaud value must be configured with the new clock fre-
quency.
The oscillator control logic has clock switch detection. If a clock switch is detected and
the Autobaud is set, the device will automatically send a Serial Break for 4096 clocks.
This will reset the Autobaud and indicate to the host that a new Autobaud character should
be sent.
23.2.7. Transmit Flow Control
Transmit flow control is implemented by the use of a remote start bit. When transmit flow
control is enabled, the transmitter will wait for the remote host to send the start bit. Trans-
mit flow control is useful in applications where receive overruns can occur.
The remote host can transmit a remote start bit by sending the character FFH. The trans-
mitter will append its data after the start bit. Due to the wire-and nature of the open drain
bus, the start bit sent by the remote host and the data bits sent by the Z8 Encore! XP F1680
Series device appear as one character; see Figure 61.
Receiving
Device
ST
Transmitting
Device
D0 D1 D2 D3 D4 D5 D6 D7 SP
Single Wire
Bus
ST D0 D1 D2 D3 D4 D5 D6 D7 SP
ST = Start bit
SP = Stop bit
D0-D7 = Data bits
Figure 61. Start Bit Flow Control
23.2.8. Breakpoints
Execution breakpoints are generated using the BRK instruction (op code 00H). When the
eZ8 CPU decodes a BRK instruction, it signals the On-Chip Debugger. If breakpoints are
enabled, the OCD idles the eZ8 CPU and enters DEBUG mode. If breakpoints are not
PS025015-1212
PRELIMINARY
On-Chip Debugger