PSD311 datasheet(13/85 Pages) STMICROELECTRONICS

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PSD3XX Family

8.0

Operating

Modes (MCU

Configurations)

The PSD3XX’s four operating modes enable it to interface directly to most 8- and 16-bit

microcontrollers with multiplexed and non-multiplexed address/data busses. The 16-bit

modes are not available to some devices; see Table 1. The following are the four operating

modes available:

t Multiplexed 8-bit address/data bus

t Multiplexed 16-bit address/data bus

t Non-multiplexed 8-bit data bus

t Non-multiplexed 16-bit data bus

Please read the section below that corresponds to your type of MCU. Then check the

appropriate Figure (3A/3B/3C/3D) to determine your pin connections. Table 3 lists the Port

connections in tabular form.

Multiplexed 8-bit address/data bus (Figure 3A)

This mode is used to interface to microcontrollers with a multiplexed 8-bit data bus. Since

the low-order address and data are multiplexed together, your MCU will output an ALE

or AS signal. The PSD3XX contains a transparent latch to demultiplex the address/data

lines internally. All you have to do is connect the ALE/AS signal and select 8-bit multiplexed

bus mode in PSDsoft. If your MCU outputs more than 16 bits of address, and you

wish to connect them to the PSD, connect A16-A18 to Port C and A19 to A19/CSI, where

applicable.

Multiplexed 16-bit address/data bus (Figure 3B)

This mode is used to interface to microcontrollers with a multiplexed 16-bit data bus. Since

the low address bytes and data are multiplexed together, your MCU will output an ALE

or AS signal. The PSD3XX contains a transparent latch to demultiplex the address/data

lines internally. All you have to do is connect the ALE/AS signal and select 8-bit multiplexed

bus mode in PSDsoft. If your MCU outputs more than 16 bits of address, and you

wish to connect them to the PSD, connect A16-A18 to Port C and A19 to A19/CSI, where

applicable.

Non-multiplexed 8-bit data bus (Figure 3C)

This mode is used to interface to microcontrollers with a non-multiplexed 8-bit data bus.

Connect the MCU’s address bus to AD0/A0-AD15/A15 on the PSD. Connect the data bus

signals of your MCU to Port A of the PSD. If your MCU outputs more than 16 bits of

address, and you wish to connect them to the PSD, connect A16-A18 to Port C and A19 to

A19/CSI, where applicable.

Non-multiplexed 16-bit data bus (Figure 3D)

This mode is used to interface to microcontrollers with a non-multiplexed 16-bit data bus.

Connect the MCU’s address bus to AD0/A0-AD15/A15 on the PSD. Connect the low byte

data bus signals of your MCU to Port A, and the high byte data output of your MCU to Port

B of the PSD. If your MCU outputs more than 16 bits of address, and you wish to connect

them to the PSD, connect A16-A18 to Port C and A19 to A19/CSI, where applicable.

For users with multiplexed MCUs that have data multiplexed on address lines other

than A0-A7 note: You can still use the PSD3XX, but you will have to connect your

data to Port A (and Port B where required), as shown in Figure 3C or 3D. That is, you will

be connecting it as if you were using a non-multiplexed MCU. In this case, you must

connect the ALE/AS signal so that the address will still be properly latched. This option is

not available on the 3X1 versions.

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