psd813f3 STMicroelectronics, psd813f3 Datasheet - Page 55

• Manufacturer Part Number: psd813f3
• Description: Flash In-system Programmable Isp Peripherals For 8-bit Mcus
• Manufacturer: STMicroelectronics

Address In Mode
For MCUs that have more than 16 address sig-
nals, the higher addresses can be connected to
Port A, B, C, and D. The address input can be
latched in the Input Macrocell (IMC) by Address
Strobe (ALE/AS, PD0). Any input that is included
in the DPLD equations for the SRAM, or primary or
secondary Flash memory is considered to be an
address input.
Data Port Mode
Port A can be used as a data bus port for a MCU
with a non-multiplexed address/data bus. The
Data Port is connected to the data bus of the MCU.
The general I/O functions are disabled in Port A if
the port is configured as a Data Port.
Figure 27. Peripheral I/O Mode
RD
PSEL0
PSEL1
VM REGISTER BIT 7
WR
PSD813F2, PSD833F2, PSD834F2, PSD853F2, PSD854F2
PSEL
DATA BUS
Peripheral I/O Mode
Peripheral I/O mode can be used to interface with
external peripherals. In this mode, all of Port A
serves as a tri-state, bi-directional data buffer for
the MCU. Peripheral I/O Mode is enabled by set-
ting Bit 7 of the VM Register to a ’1.’ Figure
shows how Port A acts as a bi-directional buffer for
the MCU data bus if Peripheral I/O Mode is en-
abled. An equation for PSEL0 and/or PSEL1 must
be written in PSDabel. The buffer is tri-stated
when PSEL0 or PSEL1 is not active.
D0 - D7
PA0 - PA7
AI02886
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