The SC511, serial and timer card houses a Z80 SIO chip, which provides two TTL serial ports for use with FTDI style serial adapter cables, and a Z80 CTC, which has four counter/timer channels.
Powering the system
Fitting jumper shunts to headers JP1 and/or JP2 connect the FTDI style 5-volt serial port’s power pin to the card’s 5 volt supply. This enables the retro computer system to be powered from the serial port, or a device connected to the serial port to be powered from this card.
Alternatively, power can be supplied from the Z50Bus.
Do not attempt to power the system from two different sources. If the system is not being powered from a serial port, then only fit a jumper shunt to JP1 or JP2 if the serial device is being powered from the system.
Serial on the Z50Bus
The Z50Bus has two lines dedicated to a serial interface. This enabled two cards to communicate via the bus rather than having to have additional cables between the cards.
Jumpers JP3 and JP4 enable one of the serial ports to be connected to the Z50Bus RX and TX lines. Each jumper has two positions: A and B. Position A links the port A signals to the bus, while position B is for the port B signals. Leave the jumper shunts off to isolate this card’s RXD and TXD signals from the Z50Bus.
Jumpers JP5 and JP6 allow the address ranges of the SIO and CTC chips to each be set to one of two options. Each chip occupies four I/O addresses. The addresses should be set to either:
|Primary||0x80 to 0x83||0x88 to 0x8B|
|Secondary||0x84 to 0x87||0x8C to 0x8F|
The primary addresses are the defaults supported by the current firmware. A second card can be added to the system with the secondary addresses selected, but there is not currently any software to support this.
The illustration below shows the default positions for the jumper shunts on JP3 to JP6.
Two FTDI style 5-volt serial ports are provided at P2 and P3.
The pin-out, below, describes signals with respect to the card, so an output is a signal from the card to a computer or terminal.
|6||Clear To Send (CTS) input to the card|
|5||Transmit Data (TxD) output from the card|
|4||Receive Data (RxD) input to the card|
|2||Request To Send (RTS) output from the card|
The serial ports settings depend on the firmware or software being run. Typically these are:
|Setting||Port A||Port B|
Current firmware assumes the use of serial port A as the default console device.
Counter / Timer
The Z80 CTC is a four-channel counter/timer interface. The channels are used as follows:
- Channel 0: Serial port A baud rate clock
- Channel 1: Serial port B baud rate clock
- Channel 2 and 3: Clock tick generator/timer
The output of channel 2 is connected to the input of channel 3. This makes a flexible clock tick generator or timer.
For full details search for Z84C30 datasheet or the Zilog Z80 Family CPU Peripherals User Manual (UM0081).
This card has its own oscillator as a clock source for the CTC, making the serial port and timer functions independent of the CPU’s main clock.
Software and Firmware Support
Z80 systems with the Small Computer Monitor in ROM:
Plug this card and a Z80 processor card, such as SC118, into a suitable backplane. Connect an FTDI style serial to USB adapter from serial port A (S1 or P2) to a computer running a terminal emulation program. The terminal should be configured for 115200 baud, 8 data, 1 stop, no parity. Flow control can be either Off or hardware RTS/CTS.
Turn the power on. The terminal should show something similar to the illustration below.
Z180 systems with RomWBW:
This card is not supported in the 3.0.1 release version of RomWBW, but you can download the latest pre-release version from the development branch and configure it for this card. Later release versions of RomWBW should include support for this card.