PSD4235G2 Datasheet, PDF (8/89 Pages) STMicroelectronics – Flash In-System Programmable ISP Peripherals For 16-bit MCUs 5V Supply

PSD4235G2
PSD ARCHITECTURAL OVERVIEW
PSD devices contain several major functional
blocks. Figure 4 shows the architecture of the PSD
device family. The functions of each block are de-
scribed briefly in the following sections. Many of
the blocks perform multiple functions and are user
configurable.
Memory
Each of the memory blocks is briefly discussed in
the following paragraphs. A more detailed discus-
sion can be found in the section entitled “Memory
Blocks“ on page 20.
The 4 Mbit primary Flash memory is the main
memory of the PSD. It is divided into 8 equally-
sized sectors that are individually selectable.
The 256 Kbit secondary Flash memory is divided
into 4 equally-sized sectors. Each sector is individ-
ually selectable.
The 64 Kbit SRAM is intended for use as a
scratch-pad memory or as an extension to the
MCU SRAM. If an external battery is connected to
the PSD’s Voltage Stand-by (VSTBY, PE6) signal,
data is retained in the event of power failure.
Each memory block can be located in a different
address space as defined by the user. The access
times for all memory types includes the address
latching and DPLD decoding time.
PLDs
The device contains two PLD blocks, the Decode
PLD (DPLD) and the Complex PLD (CPLD), as
shown in Table 2, each optimized for a different
function. The functional partitioning of the PLDs
reduces power consumption, optimizes cost/per-
formance, and eases design entry.
The DPLD is used to decode addresses and to
generate Sector Select signals for the PSD inter-
nal memory and registers. The DPLD has combi-
natorial outputs, while the CPLD can implement
more general user-defined logic functions. The
CPLD has 16 Output Macrocells (OMC) and 8
combinatorial outputs. The PSD also has 24 Input
Macrocells (IMC) that can be configured as inputs
to the PLDs. The PLDs receive their inputs from
the PLD Input Bus and are differentiated by their
output destinations, number of product terms, and
Macrocells.
The PLDs consume minimal power. The speed
and power consumption of the PLD is controlled
by the Turbo bit in PMMR0 and other bits in
PMMR2. These registers are set by the MCU at
run-time. There is a slight penalty to PLD propaga-
tion time when not in the Turbo mode.
I/O Ports
The PSD has 52 I/O pins divided among seven
ports (Port A, B, C, D, E, F and G). Each I/O pin
can be individually configured for different func-
tions. Ports can be configured as standard MCU I/
O ports, PLD I/O, or latched address outputs for
MCUs using multiplexed address/data buses
The JTAG pins can be enabled on Port E for In-
System Programming (ISP).
Table 2. PLD I/O
Name
Inputs
Outputs
Product
Terms
Decode PLD (DPLD)
82
17
43
Complex PLD (CPLD) 82
24
150
MCU Bus Interface
The PSD easily interfaces easily with most 16-bit
MCUs, either with multiplexed or non-multiplexed
address/data buses. The device is configured to
respond to the MCU’s control pins, which are also
used as inputs to the PLDs.
ISP via JTAG Port
In-System Programming (ISP) can be performed
through the JTAG signals on Port E. This serial in-
terface allows complete programming of the entire
PSD device. A blank device can be completely
programmed. The JTAG signals (TMS, TCK,
TSTAT, TERR, TDI, TDO) can be multiplexed with
other functions on Port E. Table 3 indicates the
JTAG pin assignments.
In-System Programming (ISP)
Using the JTAG signals on Port E, the entire PSD
device (memory, logic, configuration) can be pro-
grammed or erased without the use of the MCU.
Table 3. JTAG SIgnals on Port E
Port E Pins
JTAG Signal
PE0
TMS
PE1
TCK
PE2
TDI
PE3
TDO
PE4
TSTAT
PE5
TERR
In-Application Programming (IAP)
The primary Flash memory can also be pro-
grammed, or re-programmed, in-system by the
MCU executing the programming algorithms out of
the secondary Flash memory, or SRAM. The sec-
ondary Flash memory can be programmed the
same way by executing out of the primary Flash
memory. Table 4 indicates which programming
methods can program different functional blocks
of the PSD.
8/89