CDP1853

The CDP1852/3 and CDP1852C/3 are parallel, 8-bit, modeprogrammable input/output ports. They are compatible and will interface directly with CDP1800-Series microprocessors.

CDP1853 are also useful as 8-bit address latches when used with the CDP1800 multiplexed address bus and as I/O ports in general-purpose applications.

The mode control CDP1853 is used to program the device as an input port (mode = 0) or as an output port (mode = 1). The SR/SR output can be used as a signal to indicate when data is ready to be transferred. In the input mode, a peripheral device can strobe data into the CDP1852/3, and microprocessor can read that data by device selection. In the output mode, a microprocessor strobes data into the CDP1852/3, and handshaking is established with a peripheral device when the CDP1852/3 is deselected.

In the input mode CDP1853, data at the data-in terminals (DI0-DI7) is strobed into the port's 8-bit register by a high (1) level on the clock line. The negative high-to-low transition of the clock latches the data in the register and sets the service request output low (SR/SR = 0). When CS1/CS1 and CS2 are high (CS1/CS1 and CS2 = 1), the three-state output drivers are enabled and data in the 8-bit register appear at the data-out terminals (DO0-DO7). When either CS1/CS1 or CS2 goes low (CS1/CS1 or CS2 = 0), the data-out terminals are tristated and the service request output returns high (SR/SR =1).

In the output mode, the output drivers CDP1853 are enabled at all times. Data at the data-in terminals (DI0-DI7) is strobed into the 8-bit register when CS1/CS1 is low (CS1/CS1 = 0) and CS2 and the clock are high (1), and are present at the dataout terminals (DO0-DO7). The negative high-to-low transition of the clock latches the data in the register. The SR/SR output goes high (SR/SR = 1) when the device is deselected (CS1/CS1 = 1 or CS2 = 0) and returns low (SR/SR = 0) on the following trailing edge of the clock.

A CLEAR control CDP1853 is provided for resetting the port's register (DO0-DO7 = 0) and service request flip-flop (input mode: SR/SR = 1 and output mode: SR/SR = 0).

The CDP1852/3 is functionally identical to the CDP1852C/3.

The CDP1852/3 has a recommended operating voltage range of 4V to 10.5V, and the CDP1852C/3 has a recommended operating voltage range of 4V to 6.5V.

The CDP1852/3 and CDP1852C/3 are supplied in 24-lead, dual-in-line side-brazed ceramic packages (D suffix).